Remove deprecated contrib plugins (pantsbuild#9762)

Refer to https://groups.google.com/forum/#!topic/pants-devel/ngMZRIJvwHM.

[ci skip-rust-tests]
[ci skip-jvm-tests]

BUILD

@@ -16,9 +16,6 @@ files(
 files(
   name = 'build_tools',
   sources = ['BUILD.tools'],
-  dependencies = [
-    ':scalajs_3rdparty_directory',
-  ],
 )
 
 files(
@@ -31,11 +28,6 @@ files(
   sources = ['.isort.cfg'],
 )
 
-files(
-  name = 'scalajs_3rdparty_directory',
-  sources = ['contrib/scalajs/3rdparty/**/*'],
-)
-
 files(
   name = 'pants_toml',
   sources = ['pants.toml'],

BUILD.tools

@@ -1,29 +1,6 @@
 # JVM artifacts that Pants itself depends on.
 # http://pantsbuild.github.io/dev_tasks.html#jvm-tool-bootstrapping
 
-target(
-  name = 'scala-js-cli',
-  dependencies=[
-    'contrib/scalajs/3rdparty/jvm/org/scala-js:cli'
-  ],
-)
-
-target(
-  name = 'scala-js-compiler',
-  dependencies=[
-    'contrib/scalajs/3rdparty/jvm/org/scala-js:compiler',
-    'contrib/scalajs/3rdparty/jvm/org/scala-js:library',
-  ],
-)
-
-target(
-  name = 'scala-js-library',
-  dependencies = [
-    'contrib/scalajs/3rdparty/jvm/org/scala-js:library',
-  ],
-)
-
-
 # TODO: Attempting to use these targets fails because BootstrapJvmTools.get_alternate_target_roots()
 # doesn't descend into dependent target directories and uses the same build_graph it starts with.
 # target(
@@ -84,14 +61,3 @@ jar_library(
         url='https://raw.githubusercontent.com/toolchainlabs/binhost/master/java/javac/9+181-r4173-1/javac-9+181-r4173-1.jar'),
   ],
 )
-
-# Runtime dependencies for the Avro Java generated code.
-avro_rev = '1.8.2'
-
-jar_library(
-  name = 'avro-java-runtime',
-  jars = [
-    jar(org='org.apache.avro', name='avro', rev=avro_rev),
-    jar(org='org.apache.avro', name='avro-ipc', rev=avro_rev),
-  ],
-)

contrib/BUILD

@@ -4,24 +4,16 @@
 target(
   name = 'plugins',
   dependencies = [
-    'contrib/avro/src/python/pants/contrib/avro:plugin',
     'contrib/awslambda/python/src/python/pants/contrib/awslambda/python:plugin',
     'contrib/buildgen/src/python/pants/contrib/buildgen:plugin',
     'contrib/buildrefactor/src/python/pants/contrib/buildrefactor:plugin',
     'contrib/codeanalysis/src/python/pants/contrib/codeanalysis:plugin',
     'contrib/confluence/src/python/pants/contrib/confluence:plugin',
-    'contrib/cpp/src/python/pants/contrib/cpp:plugin',
-    'contrib/errorprone/src/python/pants/contrib/errorprone:plugin',
-    'contrib/findbugs/src/python/pants/contrib/findbugs:plugin',
     'contrib/go/src/python/pants/contrib/go:plugin',
-    'contrib/googlejavaformat/src/python/pants/contrib/googlejavaformat:plugin',
-    'contrib/jax_ws/src/python/pants/contrib/jax_ws:plugin',
     'contrib/mypy/src/python/pants/contrib/mypy:plugin',
     'contrib/node/src/python/pants/contrib/node:plugin',
     'contrib/python/src/python/pants/contrib/python/checks:plugin',
-    'contrib/scalajs/src/python/pants/contrib/scalajs:plugin',
     'contrib/scrooge/src/python/pants/contrib/scrooge:plugin',
-    'contrib/thrifty/src/python/pants/contrib/thrifty:plugin',
   ]
 )