Local bazelrc file approach for passing gcloud auth credentials (#329)

## Summary
Adds support for creating a new `.bazelrc.local` file specifying custom
build/test bazel options which can be used for passing gcloud auth
credentials

## Checklist
- [ ] Added Unit Tests
- [ ] Covered by existing CI
- [ ] Integration tested
- [ ] Documentation update



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Updated the build configuration to optionally load a user-specific
settings file, replacing the automatic use of preset credentials.
- **Documentation**
- Enhanced guidance with a new section detailing steps for setting up
personal authentication credentials.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: kumar-zlai

.bazelrc

@@ -1,4 +1,7 @@
+try-import %workspace%/.bazelrc.local
+
 build --java_language_version=11
 build --java_runtime_version=11
+build --remote_cache=https://storage.googleapis.com/zipline-bazel-cache
 test --test_output=errors
 test --test_timeout=900

devnotes.md

@@ -80,6 +80,13 @@ export PATH="/usr/local/bin:${PATH}"
 We enabled remote caching for all our builds/tests for both local development and CI.
 As part of that change we would need to do gcloud auth to read/write from remote cache stored in our BigTable bucket for the local dev builds.
 
+#### For passing GCloud Auth credentials to Bazel
+Create a new .bazelrc.local file with the following content. Also feel free to specify any local overrides to the build/test options here.
+This file is git-ignored.
+```
+build --google_credentials=/Users/{username}/.config/gcloud/application_default_credentials.json
+```
+
 ### Java not found error on Mac
 
 In case you run into this error the fix is to manually download and install amazon corretto-17 from [here](https://docs.aws.amazon.com/corretto/latest/corretto-17-ug/downloads-list.html)