Prepare the 2.9.0rc0 release.

[jsirois]

[ci skip-rust]

[jsirois]

Internal

• [internal] Do not import python backend from docker backend. (#13897)

• [internal] JVM only infers dependencies on artifacts in the target's resolve(s) (#13907)

• [internal] Refactor JVM artifact mapping code (#13905)

• [internal] Add compatible_resolves to jvm_artifact target (#13893)

• [internal] Skip JVM test failing with forbidden (#13901)

• [internal] Refactor jvm_artifact usage (#13890)

• [internal] Upgrade toolchain plugin to 0.16.0 (#13884)

• [internal] Fix resolve field handling for JVM (#13876)

• [internal] add TODOs for issue 13879 re compiling wrapper binaries (#13883)

• [internal] go: merge test and regular embed configurations (#13877)

• [internal] scala: refactor scalapb codegen and add JVM protoc plugin support (#13873)

• [internal] Add failing tests for Go embed not working when running tests (#13875)

• [internal] Reword and use more whitespace with JVM target type help messages (#13869)

[Eric-Arellano]

Awesome, thank you