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

[gabriele-wolfox]

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.