Summary:
Added an option to skip building extra pg extensions. For example, documentdb build is ~7-8 minutes on GCP 4-core dev-server with distributed build and is not always needed for dev purposes.

Test Plan:
- `ybd --clean --sj --force --skip-extra-pg-extensions`
- `YB_SKIP_EXTRA_PG_EXTENSIONS=1 ybd --clean --sj --force`
- `ybd --clean --sj --force`

Reviewers: hsunder, jason

Reviewed By: jason

Subscribers: jason, yql, ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D55989