updating version numbers for 2.35.0 rc

[serban-nicusor-toptal]

Submisison Checklist

• [ ] Run tests: ./runCmdStanTests.py src/test
• [ ] Declare copyright holder and open-source license: see below

Summary:

Update version numbers for 2.35.0 release. Release notes to be added later.

Intended Effect:

How to Verify:

Side Effects:

Documentation:

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company):

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)