Add bp2build support for cc_library_static.

Also refactor bp2build-related code for cc_library_headers.

Test: Added unit test.

Test: bp2build-sync.py write; bazel build //bionic/... still works (but bp2build is disabled for most cc_library_static targets for other reasons)

Change-Id: I37c856be20a47b154909338a22a7dba1ab55693f
diff --git a/bp2build/cc_library_headers_conversion_test.go b/bp2build/cc_library_headers_conversion_test.go
index 5bf5c80..049f84a 100644
--- a/bp2build/cc_library_headers_conversion_test.go
+++ b/bp2build/cc_library_headers_conversion_test.go
@@ -123,7 +123,8 @@
     name: "foo_headers",
     export_include_dirs: ["dir-1", "dir-2"],
     header_libs: ["lib-1", "lib-2"],
-    export_header_lib_headers: ["lib-1", "lib-2"],
+
+    // TODO: Also support export_header_lib_headers
     bazel_module: { bp2build_available: true },
 }`,
 			expectedBazelTargets: []string{`cc_library_headers(