scala source file should not depend on scalac plugins (pantsbuild#20971)

These are compile-time-only dependencies and should not be packaged with
the source file or included in the classpath for the source file.

In our repository, this caused a conflict because the semanticdb package
internally wraps the fastparse library with a different version than the
one we are using. There is no need for semanticdb to be packaged or run
within a test of a target; it is a compile-time-only dependency.
Moreover, the scalac compile goal handles the scalac plugins on its own
and doesn't use that.

I ran this on our Scala repository, and it compiled successfully.

docs/notes/2.23.x.md

@@ -18,6 +18,10 @@ We offer [formal sponsorship tiers for companies](https://www.pantsbuild.org/spo
 
 ### Backends
 
+#### Scala
+
+Source files no longer produce a dependency on Scala plugins. If you are using a Scala plugin that is also required by the source code (such as acyclic), please add an explicit dependency or set the `packages` field on the artifact.
+
 #### Python
 
 [The `pants.backend.experimental.python.typecheck.pyright` backend](https://www.pantsbuild.org/2.23/reference/subsystems/pyright) now uses version 1.1.365 by default.

src/python/pants/backend/scala/compile/scalac_test.py

@@ -586,6 +586,7 @@ def test_compile_with_local_scalac_plugin(
 
                 scala_sources(
                     scalac_plugins=["acyclic"],
+                    dependencies=["3rdparty/jvm:com.lihaoyi_acyclic_2.13"],
                 )
                 """
             ),
@@ -1028,6 +1029,7 @@ def test_cross_compile_with_scalac_plugin(
                 scala_sources(
                     name="main",
                     scalac_plugins=["acyclic"],
+                    dependencies=["3rdparty/jvm:acyclic"],
                     resolve=parametrize("scala2.12", "scala2.13")
                 )
                 """

src/python/pants/backend/scala/dependency_inference/rules.py

@@ -5,10 +5,6 @@
 from dataclasses import dataclass
 
 from pants.backend.scala.compile import scalac_plugins
-from pants.backend.scala.compile.scalac_plugins import (
-    ScalaPluginsForTargetWithoutResolveRequest,
-    ScalaPluginTargetsForTarget,
-)
 from pants.backend.scala.dependency_inference import scala_parser, symbol_mapper
 from pants.backend.scala.dependency_inference.scala_parser import ScalaSourceDependencyAnalysis
 from pants.backend.scala.subsystems.scala import ScalaSubsystem
@@ -28,8 +24,6 @@
     FieldSet,
     InferDependenciesRequest,
     InferredDependencies,
-    WrappedTarget,
-    WrappedTargetRequest,
 )
 from pants.engine.unions import UnionRule
 from pants.jvm.dependency_inference import artifact_mapper
@@ -119,10 +113,6 @@ class ScalaPluginDependencyInferenceFieldSet(FieldSet):
     resolve: JvmResolveField
 
 
-class InferScalaPluginDependenciesRequest(InferDependenciesRequest):
-    infer_from = ScalaPluginDependencyInferenceFieldSet
-
-
 @dataclass(frozen=True)
 class ScalaRuntimeForResolveRequest:
     resolve_name: str
@@ -172,28 +162,6 @@ async def infer_scala_library_dependency(
     return InferredDependencies(scala_library_target_info.addresses)
 
 
-@rule(desc="Infer dependency on scala plugin artifacts for Scala target.")
-async def infer_scala_plugin_dependencies(
-    request: InferScalaPluginDependenciesRequest,
-) -> InferredDependencies:
-    """Adds dependencies on plugins for scala source files, so that they get included in the
-    target's resolve."""
-
-    wrapped_target = await Get(
-        WrappedTarget,
-        WrappedTargetRequest(request.field_set.address, description_of_origin="<infallible>"),
-    )
-    target = wrapped_target.target
-
-    scala_plugins = await Get(
-        ScalaPluginTargetsForTarget, ScalaPluginsForTargetWithoutResolveRequest(target)
-    )
-
-    plugin_addresses = [target.address for target in scala_plugins.artifacts]
-
-    return InferredDependencies(plugin_addresses)
-
-
 def rules():
     return [
         *collect_rules(),
@@ -204,5 +172,4 @@ def rules():
         *versions.rules(),
         UnionRule(InferDependenciesRequest, InferScalaSourceDependencies),
         UnionRule(InferDependenciesRequest, InferScalaLibraryDependencyRequest),
-        UnionRule(InferDependenciesRequest, InferScalaPluginDependenciesRequest),
     ]