[CI] ivas-conformance 26.252 and related CI fixes

• Related issues: None
• Requested reviewers: @kiene, @pihlajakuja, @tamarapu, @malenovsky, @bohmr

Reason why this change is needed

• Implementation of 26.252

Description of the change

• Added ivas-conformance-windows, for now triggered manually
• Unification of bitstream suffixes (.192) and output audio (.wav)
• Replace random tags in FER file names with the name of the error pattern, pinging @malenovsky
• Move contents of tests/{split_}renderer/conftest.py to tests/conftest.py. This makes it simpler to include renderer tests in BASOP CI. @tamarapu
• Renderer configuration and test files moved to scripts/testv for easier bundling into conformance package.
• Some test files give paths that exceed 255 characters and fail on Windows -- shortened names in self_test.prm.
• Propagate the keep_files argument to all functions to make sure everything can be kept for the conformance test.

Affected operating points

• CI only. Should not affect any of the tests, only unify some functionality.