Add manual tag to proto_library at the root package

This is a fix similar to aosp/2707793. This adds manual tags to the
top-level proto_library created in the root package, plus any
dynamically created proto_library targets for proto.include_dirs. These
proto_library targets might not specify their deps correctly and might
be unbuildable.

(We need to keep these targets because they provide a ProtoInfo for
cc/java/py source gen)

Test: go test ./bp2build
Change-Id: Ic00f05186327fcfcc8d33a0a2c0891ed619b7acb
diff --git a/bp2build/cc_library_conversion_test.go b/bp2build/cc_library_conversion_test.go
index 28dbf7e..05d2e6a 100644
--- a/bp2build/cc_library_conversion_test.go
+++ b/bp2build/cc_library_conversion_test.go
@@ -4965,6 +4965,7 @@
 		}),
 		MakeBazelTarget("proto_library", "foo_proto", AttrNameToString{
 			"srcs": `["foo.proto"]`,
+			"tags": `["manual"]`,
 		}),
 		MakeBazelTarget("cc_lite_proto_library", "foo_cc_proto_lite", AttrNameToString{
 			"deps": `[
@@ -5033,6 +5034,7 @@
 		MakeBazelTarget("proto_library", "foo_proto", AttrNameToString{
 			"srcs":                `["foo.proto"]`,
 			"strip_import_prefix": `""`,
+			"tags":                `["manual"]`,
 		}),
 		MakeBazelTarget("cc_lite_proto_library", "foo_cc_proto_lite", AttrNameToString{
 			"deps": `[
@@ -5103,6 +5105,7 @@
 		}),
 		MakeBazelTarget("proto_library", "foo_proto", AttrNameToString{
 			"srcs": `["foo.proto"]`,
+			"tags": `["manual"]`,
 		}),
 		MakeBazelTarget("cc_lite_proto_library", "foo_cc_proto_lite", AttrNameToString{
 			"deps": `[":foo_proto"]`,