chore: remove duplicate per-package contribution and license files (#7972)

* chore: remove duplicate per-package contribution and license files

* fix(area120-tables): skip failing quickstart test

* fix(storage-control): type conflict between @sinonjs/fake-timers and @types/sinonjs__fake-timers

* fix(apigeeregistry): skip failing quickstart test

* Revert recent test skips and dependency overrides

This reverts the following commits because the issues were fixed externally:
- 4671b3f: fix(apigeeregistry): skip failing quickstart test
- ae52412: fix(storage-control): type conflict between @sinonjs/fake-timers and @types/sinonjs__fake-timers
- 1ee8974: fix(area120-tables): skip failing quickstart test

* chore: prevent gapic generator from copying root-level files into packages

To prevent `LICENSE`, `CONTRIBUTING.md`, and `CODE_OF_CONDUCT.md` from being re-added to individual packages after they were removed in PR #..., this updates the gapic generator templates to stop generating them.
Also updates `README.md.njk` to point to the root-level `LICENSE` and `CONTRIBUTING.md`.

---------

Co-authored-by: Gabe Pearhill <86282859+pearigee@users.noreply.github.com>

Author: GautamSharda

core/generator/gapic-generator-typescript/baselines/asset-esm/CODE_OF_CONDUCT.md.baseline

@@ -86,7 +86,7 @@ More Information: [Google Cloud Platform Launch Stages][launch_stages]
 
 ## Contributing
 
-Contributions welcome! See the [Contributing Guide](https://github.com/googleapis/google-cloud-node/blob/main/packages/google-cloud-asset/CONTRIBUTING.md).
+Contributions welcome! See the [Contributing Guide](https://github.com/googleapis/google-cloud-node/blob/main/CONTRIBUTING.md).
 
 Please note that this `README.md`
 and a variety of configuration files in this repository (including `.nycrc` and `tsconfig.json`)
@@ -96,7 +96,7 @@ are generated from a central template.
 
 Apache Version 2.0
 
-See [LICENSE](https://github.com/googleapis/google-cloud-node/blob/main/packages/google-cloud-asset/LICENSE)
+See [LICENSE](https://github.com/googleapis/google-cloud-node/blob/main/LICENSE)
 
 [shell_img]: https://gstatic.com/cloudssh/images/open-btn.png
 [projects]: https://console.cloud.google.com/project