Remove hardcoded argument from autoflake linter

Move "--remove-all-unused-imports" to a default argument rather than a hardcoded
portion of the command for autoflake. This allows a user to override if the'd
prefer a more conservative run of autoflake.

src/python/pants/backend/python/lint/autoflake/rules.py

@@ -47,7 +47,6 @@ async def autoflake_fmt(request: AutoflakeRequest, autoflake: Autoflake) -> FmtR
             autoflake_pex,
             argv=(
                 "--in-place",
-                "--remove-all-unused-imports",
                 *autoflake.args,
                 *request.snapshot.files,
             ),

src/python/pants/backend/python/lint/autoflake/subsystem.py

@@ -33,7 +33,10 @@ class Autoflake(PythonToolBase):
     default_lockfile_url = git_url(default_lockfile_path)
 
     skip = SkipOption("fmt", "lint")
-    args = ArgsListOption(example="--target-version=py37 --quiet")
+    args = ArgsListOption(
+        example="--remove-all-unused-imports --target-version=py37 --quiet",
+        default=["--remove-all-unused-imports"],
+    )
     export = ExportToolOption()
 
 

src/python/pants/option/option_types.py

@@ -789,6 +789,7 @@ def __new__(
         # This should be set when callers can alternatively use "--" followed by the arguments,
         # instead of having to provide "--[scope]-args='--arg1 --arg2'".
         passthrough: bool | None = None,
+        default: list[str] | None = None,
     ):
         if extra_help:
             extra_help = "\n\n" + extra_help