Reduce PreCommit test to the minimum and move rest of them to PostCommit one

To reduce resource usage for PreCommit tests, these needs are to be met.
- For low-priority Python, tests only in the typehints package are run when PreCommit test called. And rest of them are moved to the PostCommit one.
- For high-priority Python, PreCommit and PostCommit tests are AS IS.
- Assured that we can add more tests easily later if there is a need.
e.g. using filepath to identify which tests to run

Imported from Jira [BEAM-9944](https://issues.apache.org/jira/browse/BEAM-9944). Original Jira may contain additional context.
Reported by: yoshiki.obata.
Subtask of issue #20207

Start with issue #20207, then inspect the existing PreCommit and PostCommit test selection for Python, especially the typehints package and any filepath-based selection. Done means low-priority Python PreCommit runs only typehints tests, the remaining tests run in PostCommit, high-priority tests remain unchanged, and adding future selections is straightforward.

Written by the indexing model from the issue text.