fix(risedev): CONNECTOR_LIBS_PATH for frontend is not set

[xxchan]

I hereby agree to the terms of the RisingWave Labs, Inc. Contributor License Agreement.

What's changed and what's your intention?

refactor to bring common env vars together.

Found while testing iceberg engine
https://github.com/risingwavelabs/risingwave/blob/xxchan/unpleasant-catshark/src/frontend/src/handler/create_table.rs#L1743

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• My PR contains critical fixes that are necessary to be merged into the latest release.

Documentation

• My PR needs documentation updates.

Release note

[BugenZhao]

refactor to bring common env vars together.

Cool