Potential performance regressions in pkg/ccl/pgcryptoccl/pgcryptocipherccl

These were originally routed to CDC, I'm creating this issue so they can be tracked separately since pgcryptoccl is owned by SQL Foundations

[performance regression](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_RoachprodMicrobenchmarkWeeklyWip/20958673?buildTab=log) on master @ [94a1e22436ad935d8c7f9524cb8fc0fd7b24faaa](https://github.com/cockroachdb/cockroach/commits/94a1e22436ad935d8c7f9524cb8fc0fd7b24faaa):

Performance regressions detected in package pkg/ccl

Comparison: v25.4.2 (https://github.com/cockroachdb/cockroach/commit/2c80e22e93a1fc4e9c268fa7b6c2018acfa09724) -> refs/heads/master (https://github.com/cockroachdb/cockroach/commit/94a1e22436ad935d8c7f9524cb8fc0fd7b24faaa)

Found 6 benchmark(s) with regressions ≥20%:

- [ ] [pkg/ccl/pgcryptoccl/pgcryptocipherccl→Encrypt/AES-128_with_IV-32 (B/op): +49.88% (49.9%)](https://microbench.testeng.crdb.io/dashboard/?benchmark=Encrypt/AES-128_with_IV-32&package=pkg/ccl/pgcryptoccl/pgcryptocipherccl)

- [ ] [pkg/ccl/pgcryptoccl/pgcryptocipherccl→Encrypt/AES-128-32 (B/op): +48.90% (48.9%)](https://microbench.testeng.crdb.io/dashboard/?benchmark=Encrypt/AES-128-32&package=pkg/ccl/pgcryptoccl/pgcryptocipherccl)

- [ ] [pkg/ccl/pgcryptoccl/pgcryptocipherccl→Encrypt/AES-256-32 (B/op): +39.12% (39.1%)](https://microbench.testeng.crdb.io/dashboard/?benchmark=Encrypt/AES-256-32&package=pkg/ccl/pgcryptoccl/pgcryptocipherccl)

- [ ] [pkg/ccl/pgcryptoccl/pgcryptocipherccl→Encrypt/AES-192-32 (B/op): +32.95% (32.9%)](https://microbench.testeng.crdb.io/dashboard/?benchmark=Encrypt/AES-192-32&package=pkg/ccl/pgcryptoccl/pgcryptocipherccl)

- [ ] [pkg/ccl/pgcryptoccl/pgcryptocipherccl→Encrypt/AES-192_with_IV-32 (B/op): +32.95% (32.9%)](https://microbench.testeng.crdb.io/dashboard/?benchmark=Encrypt/AES-192_with_IV-32&package=pkg/ccl/pgcryptoccl/pgcryptocipherccl)

- [ ] [pkg/ccl/pgcryptoccl/pgcryptocipherccl→Encrypt/AES-256_with_IV-32 (B/op): +21.96% (22.0%)](https://microbench.testeng.crdb.io/dashboard/?benchmark=Encrypt/AES-256_with_IV-32&package=pkg/ccl/pgcryptoccl/pgcryptocipherccl)

Jira issue: CRDB-58699