sql,server: support SCRAM authentication for SQL sessions

[cockroach-teamcity]

Exalate commented:

cockroachdb/cockroach#74301 --- Release note (backward-incompatible change): The environment variable that controls the max amount of CPU that can be taken by password hash computations during authentication was renamed from COCKROACH_MAX_BCRYPT_CONCURRENCY to COCKROACH_MAX_PW_HASH_COMPUTE_CONCURRENCY. Its semantics remain unchanged. Release note (security update): CockroachDB is now able to authenticate users via the web UI and through SQL sessions when the client provides a cleartext password and the stored credentials are encoded using the SCRAM-SHA-256 algorithm. (Note: support for a SCRAM authentication flow is a separate feature and is not the target of this release note.) In particular, for SQL client sessions it makes it possible to use the authentication methods password (cleartext passwords), and cert-password (TLS client cert or cleartext password) with either CRDB-BCRYPT or SCRAM-SHA-256 stored credentials. Previously, only CRDB-BCRYPT stored credentials were supported for cleartext password authentication.

Jira Issue: DOC-2362

[rafiss]

covered by #12792