Add e2e test of recover backups with mixed compression across tier1 and tier2

Add an e2e test that recovers backups taken with different Kopia compression algorithms configured per tier, verifying recovery succeeds
regardless of the algorithm used at backup time.

- Configure tier1 and tier2 with different `compression.algorithm` values (e.g. `zstd` and `s2-default`) via `PluginConfiguration`.
- Take backups under each configuration.
- Recover from both tier1 and tier2 backups and verify data integrity.

Existing `Compression` feature scenario (`operator/test/e2e/compression_test.go`) only verifies the algorithm is applied to the Kopia repo config; it does not exercise backup/recovery.