Finalization bugfixes.

- keep previous platform versions in platform_releases.txt,
- fix for the build version test,
- after discussion with Yuri, keep non-REL resource sdk_int the same.

Bug: 323940469
Test: local run
Ignore-AOSP-First: release configs present in internal repo only
Change-Id: I6637e109191480ded615ef35c9185d927ddaec40