Adds SentinelUsername and SentinelPassword fields to redis.Config and wires
them through to goredis.UniversalOptions.

In security-hardened deployments, Sentinel processes authenticate independently
from Redis data nodes. Previously, callers had no way to supply Sentinel-tier
credentials through the labkit client.

Modifies the v2/redis integration tests to only run on changes to the
redis package and go.[mod|sum].

Modifies the v2/postgres integration test to only run on changes to the
postgres package and go.[mod|sum].

Always run integration tests on master branch

ci: selectively run integration tests on file changes

See merge request !506

Merged-by: Matias Alvarez <malvarez@gitlab.com>
Approved-by: Matias Alvarez <malvarez@gitlab.com>
Reviewed-by: GitLab Duo <gitlab-duo@gitlab.com>
Co-authored-by: Luke Hollinda <lhollinda@gitlab.com>

feat(v2/redis): add SentinelUsername and SentinelPassword to Config

See merge request !500

Merged-by: Matias Alvarez <malvarez@gitlab.com>
Approved-by: Suleimi Ahmed <sahmed@gitlab.com>
Approved-by: Matias Alvarez <malvarez@gitlab.com>
Reviewed-by: GitLab Duo <gitlab-duo@gitlab.com>
Reviewed-by: Matias Alvarez <malvarez@gitlab.com>
Co-authored-by: Luke Hollinda <lhollinda@gitlab.com>