chore(librarian): fix generation for google-cloud-compute (#14612)

This PR resolves the following stack trace when generating
google-cloud-compute

```

Traceback (most recent call last):
  File "/app/./cli.py", line 532, in handle_generate
    _generate_api(api_path, library_id, source, output, version)
  File "/app/./cli.py", line 761, in _generate_api
    py_gapic_config = _read_bazel_build_py_rule(api_path, source)
  File "/app/./cli.py", line 556, in _read_bazel_build_py_rule
    result = parse_googleapis_content.parse_content(content)
  File "/app/parse_googleapis_content.py", line 133, in parse_content
    sl.eval(mod, ast, glb, sl.FileLoader(load))
starlark.StarlarkError: error: Variable `exports_files` not found
 --> BUILD.bazel:6:1
  |
6 | exports_files(glob(include = ["*grpc_service_config.json"]))
  | ^^^^^^^^^^^^^
  |


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/app/./cli.py", line 1406, in <module>
    args.func(
  File "/app/./cli.py", line 538, in handle_generate
    raise ValueError("Generation failed.") from e
ValueError: Generation failed.
```

Author: parthea

.generator/parse_googleapis_content.py

@@ -95,8 +95,15 @@
     "proto_library",
     "java_proto_library",
     "genrule",
+    "gapic_yaml_from_disco",
+    "grpc_service_config_from_disco",
+    "proto_from_disco",
 )
 
+_GLOB_CALLABLES = (
+    "exports_files",
+    "glob",
+)
 
 def parse_content(content: str) -> dict:
     """Parses content from BUILD.bazel and returns a dictionary
@@ -119,11 +126,20 @@ def bazel_target(**args):
     def noop_bazel_rule(**args):
         pass
 
-    for noop_callable in _NOOP_CALLABLES:
-        mod.add_callable(noop_callable, noop_bazel_rule)
+    def fake_glob(paths=[], **args):
+        return []
+
+    mod.add_callable("package", noop_bazel_rule)
+
+    for glob_callable in _GLOB_CALLABLES:
+        mod.add_callable(glob_callable, fake_glob)
 
     def load(name):
         mod = sl.Module()
+
+        for noop_callable in _NOOP_CALLABLES:
+            mod.add_callable(noop_callable, noop_bazel_rule)
+
         for callable_name in _CALLABLE_MAP.get(name, []):
             mod.add_callable(callable_name, bazel_target)
         return mod.freeze()

.generator/test-resources/librarian/BUILD.bazel

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 package(default_visibility = ["//visibility:public"])
+exports_files(glob(["*.yaml"]))
 load("@rules_proto//proto:defs.bzl", "proto_library")
 load(
     "@com_google_googleapis_imports//:imports.bzl",