Revert "Revert "Remove legacy-test and legacy-android-test targets""

Fixes up the android.test.legacy target to stop using sources directly
now that the issue with android.test.runner-minus-junit not being able
to be built against the SDK has been resolved.

Also, fixes a couple of comments.

This reverts commit 7d7af10dc9.

Reason for revert: When this was originally applied it broke the
pi-dev-plus-aosp branch as it contained references to these targets.
Those references have now been removed.

Bug: 63127064
Change-Id: I619e92faf4cc38f8fd4f053bde832e9a76a2a2bf
Test: make checkbuild

test-mock/Android.bp

@@ -30,19 +30,3 @@ java_sdk_library {
     srcs_lib_whitelist_pkgs: ["android"],
     compile_dex: true,
 }
-
-// Build the android.test.mock_static library
-// ==========================================
-// This is only intended for inclusion in the legacy-android-test.
-// Must not be used elewhere.
-java_library_static {
-    name: "android.test.mock_static",
-
-    java_version: "1.8",
-    srcs: ["src/**/*.java"],
-
-    no_framework_libs: true,
-    libs: [
-        "framework",
-    ],
-}