Account for encrypted reasoning for auto compaction (#7113)

- The total token used returned from the api doesn't account for the
reasoning items before the assistant message
- Account for those for auto compaction
- Add the encrypted reasoning effort in the common tests utils
- Add a test to make sure it works as expected

codex-rs/core/tests/common/Cargo.toml

@@ -9,6 +9,7 @@ path = "lib.rs"
 [dependencies]
 anyhow = { workspace = true }
 assert_cmd = { workspace = true }
+base64 = { workspace = true }
 codex-core = { workspace = true }
 codex-protocol = { workspace = true }
 notify = { workspace = true }