303434307: Enable flagged API checking

Also downgrade the new UseSdkSuppress check from error to warning.
And temporarily downgrades FlaggedApi from error to warning until
existing violations are resolved.

Test: The build
Bug: 303434307
Change-Id: Id7802621d567815470dee1aeb815abe214f098cd

java/lint.go

@@ -491,6 +491,7 @@ func (l *linter) lint(ctx android.ModuleContext) {
 
 	cmd.BuiltTool("lint").ImplicitTool(ctx.Config().HostJavaToolPath(ctx, "lint.jar")).
 		Flag("--quiet").
+		Flag("--include-aosp-issues").
 		FlagWithInput("--project ", lintPaths.projectXML).
 		FlagWithInput("--config ", lintPaths.configXML).
 		FlagWithOutput("--html ", html).

java/lint_defaults.txt

@@ -122,6 +122,10 @@
 --warning_check RemoteViewLayout
 --warning_check SupportAnnotationUsage
 --warning_check UniqueConstants
+--warning_check UseSdkSuppress
+# TODO(b/303434307) The intent is for this to be set to error severity
+# once existing violations are cleaned up
+--warning_check FlaggedApi
 
 # TODO(b/294098365): these checks fail in AOSP, but pass downstream
 --warning_check ForegroundServiceType