Summary:
Per our coding style ([Log Levels](https://docs.yugabyte.com/preview/contribute/core-database/coding-style/#log-levels)), we should avoid using `LOG(ERROR)`.

- For **expected failures**, use `LOG(WARNING)`.
- For **unexpected failures**, prefer `LOG(DFATAL)` to ensure tests fail appropriately.

Updated most of `LOG(ERROR)` usages to either `LOG(WARNING)` or `LOG(DFATAL)`.
Left several places where `LOG(ERROR)` is used.
Because this log is triggered in some tests, but should never happen in production.
Jira: DB-16515

Test Plan: Jenkins

Reviewers: hsunder, mlillibridge

Reviewed By: hsunder

Subscribers: jason, mlillibridge, yql, ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D43680