Allow silencing triaged warnings

### Description of the feature request:

Allow the root module to control which WARNING, INFO, and DEBUG messages should be silenced.

### Which category does this issue belong to?

CLI

### What underlying problem are you trying to solve with this feature?

When I invoke Bazel to build my project, I often get warnings from external dependencies. Some of these warnings are actionable: I appreciate them and fix them! Others I have reviewed and decided I should take no action on. Maybe the warning is a false positive (https://github.com/bazelbuild/bazel/issues/7157, NB still not fixed!), or I'm already tracking fixing it in an issue and don't need it displayed to every developer on my project. I wish I could silence these triaged warnings.

https://bazel.build/reference/command-line-reference#flag--ui_event_filters is the best we have today, but it's a blunt tool: AFAIK it only lets me silence _all_ WARNING, DEBUG, or INFO messages. That's too coarse! I want to silence specific warnings that I've triaged.

### Which operating system are you running Bazel on?

Linux and MacOS

### What is the output of `bazel info release`?

8.1.0

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse HEAD` ?

```text

```

### Have you found anything relevant by searching the web?

_No response_

### Any other information, logs, or outputs that you want to share?

_No response_

Start with the --ui_event_filters command-line reference and the issue's examples of WARNING, INFO, and DEBUG messages. Determine how a root module could identify and suppress only triaged messages while preserving actionable output; done means specific selected warnings can be silenced without suppressing all messages of their severity.

Written by the indexing model from the issue text.