proxy: Unify local and remote conn pool client structures

[awarus]

Unify client, EndpointConnPool and DbUserConnPool for remote and local conn.

• Use new ClientDataEnum for additional client data.
• Add ClientInnerCommon client structure.
• Remove Client and EndpointConnPool code from local_conn_pool.rs

Problem

Summary of changes

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

5328 tests run: 5106 passed, 0 failed, 222 skipped (full report)

---

Code coverage* (full report)

• functions: 31.6% (7791 of 24691 functions)
• lines: 49.0% (61134 of 124737 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
8535107 at 2024-11-05T15:17:23.695Z :recycle:}

[conradludgate]

looking good

[conradludgate]

lgtm thanks