chore(hermetic-build): include .github template updates as part of generation (googleapis#3723)

Part of the fix for
googleapis#3701 ☕

### Approach
The templates come from
https://github.com/googleapis/synthtool/tree/bf182cd41d9a7de56092cafcc7befe6b398332f6.
The only update was to include `generated-files-bot`, which is already
up to date in all the HW repos.

The `.kokoro` folder will be a separate follow up task. We will now
focus on solving the update of `update_generation_config` `yaml` and
`sh` files.

The fix to include the `.github` folder follows from
https://setuptools.pypa.io/en/latest/userguide/datafiles.html:
```
Glob patterns do not automatically match dotfiles, i.e., directory or file names starting with a dot (.).
To include such files, you must explicitly start the pattern with a dot, e.g. .* to match .gitignore.
```


Interestingly, this is also the reason `cp
synthool/gcp/templates/java_library/* ...` did not bring folders
starting with dot (such as .kokoro) into
googleapis#2884
### Confirming effects in downstream repos
Demos show the results as of
googleapis@b66af92
in
 - googleapis/java-storage#3012
 - googleapis/java-logging#1787
 - googleapis/java-pubsub#2384
 - googleapis/java-bigtable#2546
 - googleapis/java-spanner#3711
 - googleapis/java-firestore#2065
 - googleapis/java-datastore#1810
 - googleapis/java-bigquerystorage#2929
 - googleapis/java-pubsublite#1837

There were no regressions on templated files that were manually
modified.

Author: diegomarquezp

hermetic_build/DEVELOPMENT.md

@@ -130,6 +130,9 @@ owl-bot copy-code --version
 The key step is `npm link`, which will make the command available in you current
 shell session.
 
+If you get a permission denied error when running the command `owl-bot`, try
+relinking owl-bot by running `npm unlink -g` and re-running the steps above.
+
 ## Run the script
 The entrypoint script (`hermetic_build/library_generation/cli/entry_point.py`)
 allows you to generate a GAPIC repository with a given api definition (proto,
@@ -153,12 +156,14 @@ export path_to_repo="$(pwd)/google-cloud-java"
 ### Install the scripts
 
 You can skip this step if you've installed the packages in [Install package dependencies](#install-package-dependencies).
+Use the `--editable` flag for your changes to take effect as soon as you modify any file inside
+the package.
 
 ```shell
 python -m pip install --require-hashes -r hermetic_build/common/requirements.txt
-python -m pip install hermetic_build/common
+python -m pip install --editable hermetic_build/common
 python -m pip install --require-hashes -r hermetic_build/library_generation/requirements.txt
-python -m pip install hermetic_build/library_generation
+python -m pip install --editable hermetic_build/library_generation
 ```
 
 ### Run the script
@@ -212,10 +217,19 @@ python hermetic_build/library_generation/cli/entry_point.py generate \
         --api-definitions-path=/workspace/apis
    ```
 
-# Debug the library generation container
+# Debugging tips
+## Debug the scripts
+Especially on local setups, consider adding the `xtrace` (`set -x`) flag to
+ - `hermetic_build/library_generation/generate_library.sh`
+ - `hermetic_build/library_generation/utils/utilities.sh`
+
+This will allow you to observe how the tools you prepared in `~/.library_generation` are being used.
+
+
+## Debug the library generation container
 If you are working on changing the way the containers are created, you may want
 to inspect the containers to check the setup.
-It would be convenient in such case to have a text editor/viewer available. 
+It would be convenient in such case to have a text editor/viewer available.
 You can achieve this by modifying the Dockerfile as follows:
 
 ```dockerfile

hermetic_build/library_generation/owlbot/templates/java_library/.github/CODEOWNERS

@@ -0,0 +1,13 @@
+externalManifests:
+- type: json
+  file: 'synth.metadata'
+  jsonpath: '$.generatedFiles[*]'
+- type: json
+  file: '.github/readme/synth.metadata/synth.metadata'
+  jsonpath: '$.generatedFiles[*]'
+ignoreAuthors:
+- 'cloud-java-bot'
+- 'renovate-bot'
+- 'yoshi-automation'
+- 'release-please[bot]'
+- 'gcf-owl-bot[bot]'

hermetic_build/library_generation/owlbot/templates/java_library/.github/generated-files-bot.yml

@@ -24,6 +24,10 @@
             "owlbot/src/poms/*.py",
             "owlbot/templates/clirr/*.j2",
             "owlbot/templates/poms/*.j2",
+            "owlbot/templates/java_library/.github/**/*",
+            # TODO: uncomment this line after https://github.com/googleapis/sdk-platform-java/pull/3723
+            # has been merged.
+            # "owlbot/templates/java_library/.kokoro/**/*",
             "owlbot/templates/java_library/**/*",
         ],
         "synthtool": ["owlbot/synthtool/**/*"],