Add missing rules_java stanza to WORKSPACE

Bazel 6.5.0 fails with (fixed in the next commit):

```txt
$ bazel build //{src,jmh,test,third_party,scala_proto}/...

[ ...snip... ]

ERROR: test/src/main/resources/java_sources/BUILD:11:14:
  Building test/src/main/resources/java_sources/CompiledWithJava11_java.jar
  (1 source file) failed: Worker process did not return a WorkResponse:

---8<---8<--- Start of log, file at .../bazel-workers/multiplex-worker-33-Javac.log ---8<---8<---
Error thrown by worker thread, shutting down worker.
  java.lang.UnsupportedClassVersionError:
  com/google/errorprone/ErrorProneError has been compiled by a more
  recent version of the Java Runtime (class file version 61.0), this
  version of the Java Runtime only recognizes class file versions up to
  55.0
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    [ ...snip... ]

ERROR: test/src/main/resources/java_sources/BUILD:5:14:
  Building test/src/main/resources/java_sources/CompiledWithJava8_java.jar
  (1 source file) failed: Worker process did not return a WorkResponse:

---8<---8<--- Start of log, file at .../bazel-workers/multiplex-worker-33-Javac.log ---8<---8<---
Error thrown by worker thread, shutting down worker.
  java.lang.UnsupportedClassVersionError:
  com/google/errorprone/ErrorProneError has been compiled by a more
  recent version of the Java Runtime (class file version 61.0), this
  version of the Java Runtime only recognizes class file versions up to
  55.0
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    [ ...snip... ]
```

Bazel 7.4.1 builds.

Bazel 8.0.0rc6 fails as described in bazel-contrib#1652:

```txt
$ USE_BAZEL_VERSION=8.0.0rc6 bazel build --enable_workspace \
    //{src,jmh,test,third_party,scala_proto}/...

ERROR: Traceback (most recent call last):
  File "scala/private/common_attributes.bzl", line 18, column 28, in <toplevel>
    "deps": attr.label_list(

Error in label_list:
  Illegal argument: element in 'providers' is of unexpected type.
  Either all elements should be providers,
  or all elements should be lists of providers,
  but got list with an element of type NoneType.

ERROR: Error computing the main repository mapping:
  at .../scala/scala.bzl:45:5:
  at .../scala/private/rules/scala_repl.bzl:5:5:
initialization of module 'scala/private/common_attributes.bzl' failed
```

Bazel 8.0.0rc7 fails with a cyclic dependency error:

```txt
**ERROR:** Failed to load Starlark extension '@@rules_java//toolchains:toolchain_utils.bzl'.

Cycle in the workspace file detected. This indicates that a repository is used prior to being defined.

The following chain of repository dependencies lead to the missing definition.

 - @@rules_java
```

Author: mbland

WORKSPACE

@@ -43,6 +43,14 @@ load("//scala:scala.bzl", "scala_toolchains")
 
 scala_toolchains(fetch_sources = True)
 
+load(
+    "@rules_java//java:repositories.bzl",
+    "rules_java_dependencies",
+    "rules_java_toolchains",
+)
+rules_java_dependencies()
+rules_java_toolchains()
+
 register_toolchains(
     "//testing:testing_toolchain",
     "//scala:unused_dependency_checker_error_toolchain",