Expand buf lint PROTOVALIDATE rule to lint example and shared rules

[oliversun9]

WIP: Address TODOs and add tests

This updates the PROTOVALIDATE rule in buf lint to provide checks for two new features:

• For the protovalidate examples feature, check:
  • example values satisfy the constraints (builtin + cel)
  • if no constraint is defined on the field, an example value should not be present
• For the predefined rules feature, check:
  • a predefined rule compiles (the expression defined on buf.validate.*Rules compiles)
  • example values also satisfy any predefined rules

The protovalidate test dependency has also been updated and some previous integration tests have also been updated to reflect this.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 27, 2024, 11:07 PM

[doriable]

@rodaine Just wondering if there is a better way to do this and/or if protovalidate-go exposes some mechanism for me to resolve the "type of rule" based on the rule message descriptor (e.g. StringRules). The context of this is that, we are parsing predefined rules from our files, and then checking their CEL expressions. And so we need the type for the extension itself (which is easy, we use the celext function you and @oliversun9 exported a while ago) and we also need the type for the rule that the extension is extending.