replace json-iterator/go with reflection-free dependency to reenable dead code elimination

[kruskall]

Component(s)

pdata

What happened?

Describe the bug

any binary that depends on go.opentelemetry.io/collector/pdata has DCE (dead code elimination) disabled due to a dependency on https://github.com/json-iterator/go

Any use of reflect.Value.MethodByName() or reflect.Type.MethodByName() disables DCE. The compiler assumes that these functions will look any method up, and cannot remove methods even if they are never called.

Steps to reproduce

build a binary that depends on go.opentelemetry.io/collector/pdata

What did you expect to see?

a small binary

What did you see instead?

a huge binary

Collector version

anything after #4986

Environment information

Environment

OS: (e.g., "Ubuntu 20.04")
Compiler(if manually compiled): (e.g., "go 14.2")

OpenTelemetry Collector configuration

Log output

Additional context

No response

[github-actions]

Pinging code owners:

• pdata: @bogdandrutu @dmitryax

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