feat(crewai): support tracing crewAI (#12497)

[MLOB-2281]
This PR adds tracing and LLMObs tracing support for the CrewAI library.

[CrewAI](https://docs.crewai.com/concepts/crews) is a LLM agentic
workflow framework which involves crews (top level concept) that
accomplish a list of tasks using a set of agents (which have their own
set of tools and LLMs to accomplish said tasks with).

### Tracing
This integration patches (and traces) the following methods in CrewAI:
- `Crew.kickoff()` which encapsulates the overall crew (workflow)
execution.
- `Task._execute_core()` which encapsulates the task execution (both
sync and async)
- `Task.execute_async()` does not get traced, but we do extract the
active ddtrace/llmobs contexts to then propagate in an async thread's
invocation of `Task._execute_core()` to ensure async tracing propagates
contexts correctly.
- `Agent.execute_task()` which encapsulates the agent's execution of a
given task.
- `CrewStructuredTool.invoke()` which encapsulates a tool invocation.
- `Crew._get_context()` does not get traced, but we use this to set span
links between task execution (llmobs-specific).

### Span Linking (private preview)
**note:** Span linking only happens if llmobs is enabled and span
linking feature flag is enabled for the customer.
Span linking in CrewAI aims to infer and declare causal/input-output
relationships between spans in a trace. This PR implements the
following:
- Input-input and output-output linking from a crew span to its first
task span, and its last task span to the crew span.
- output-input linking from a task span to the next task span.
- input-input and output-output linking from a task span to its first
agent span, and its last agent span to the task span. (Note: this is
assuming that a task is accomplished only by one agent.)
- input-input and output-output linking from a tool span to its first
agent span (usually only if used in a hierarchical crew process with a
managing LLM/agent delegating tasks to other agents)

### Next steps:
- Add span linking at the bottom tool/llm level. However, this is a
challenge as llm spans can come from external integrations (i.e. openai,
anthropic, gemini) and we don't have the shared contextual information
in these cases to link these spans.

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)


[MLOB-2281]:
https://datadoghq.atlassian.net/browse/MLOB-2281?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: Yun-Kim

.github/CODEOWNERS

@@ -153,6 +153,8 @@ ddtrace/contrib/internal/vertexai                       @DataDog/ml-observabilit
 ddtrace/contrib/_vertexai.py                            @DataDog/ml-observability
 ddtrace/contrib/internal/langgraph                      @DataDog/ml-observability
 ddtrace/contrib/_langgraph.py                           @DataDog/ml-observability
+ddtrace/contrib/internal/crewai                         @DataDog/ml-observability
+ddtrace/contrib/_crewai.py                              @DataDog/ml-observability
 tests/llmobs                                            @DataDog/ml-observability
 tests/contrib/openai                                    @DataDog/ml-observability
 tests/contrib/langchain                                 @DataDog/ml-observability
@@ -164,6 +166,7 @@ tests/contrib/anthropic                                 @DataDog/ml-observabilit
 tests/contrib/google_generativeai                       @DataDog/ml-observability
 tests/contrib/vertexai                                  @DataDog/ml-observability
 tests/contrib/langgraph                                 @DataDog/ml-observability
+tests/contrib/crewai                                    @DataDog/ml-observability
 .gitlab/tests/llmobs.yml                                @DataDog/ml-observability
 
 # Remote Config

.riot/requirements/1ce4995.txt

@@ -0,0 +1,166 @@
+#
+# This file is autogenerated by pip-compile with Python 3.11
+# by the following command:
+#
+#    pip-compile --allow-unsafe --no-annotate --resolver=backtracking .riot/requirements/1ce4995.in
+#
+aiohappyeyeballs==2.6.1
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+yarl==1.18.3
+zipp==3.21.0

.riot/requirements/8b7e1b6.txt

@@ -0,0 +1,166 @@
+#
+# This file is autogenerated by pip-compile with Python 3.12
+# by the following command:
+#
+#    pip-compile --allow-unsafe --no-annotate .riot/requirements/8b7e1b6.in
+#
+aiohappyeyeballs==2.6.1
+aiohttp==3.11.14
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