Log database duration per database [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

As part of &5759 we're preparing the GitLab application to handle connections to multiple databases. As such we want to improve our observability to understand these multiple databases.

This MR is a first step which will break down the total database duration of a request by the database name of the database connection. At present this will only be 1 extra field (gitlabhq_production on production) but in future it will automatically start logging information about the other databases we add.

We assume that database name should be sufficient for distinguishing these connections in our logs for the time being. Technically we could be conneting to multiple database servers with the same database name but we don't plan on doing that first up and we can come up with a different way to identify hosts with the same database name later if that becomes necessary.

Screenshots (strongly suggested)

 {
   ...
   "db_primary_count": 0,
   "db_primary_cached_count": 0,
   "db_primary_wal_count": 0,
   "db_primary_duration_s": 0,
   "db_replica_duration_s": 0.002,
+  "db_replica_gitlabhq_development_duration_s": 0.002,
   "cpu_s": 9.344601,
   "queue_duration_s": 0.34234,
   ...
 }

Does this MR meet the acceptance criteria?

Conformity

• [-] I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• [-] I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #332946 (closed)