📖 Improve Linting Workflow to only lint relevant files to a PR

[jhpyke]

User Story

As a user of the repo
I expect to not wait 8 to 25(!) minutes for my PR to be linted
So that I can do my work in a reasonable amount of time.

Value / Purpose

This should speed up workflows for users, as well as cutting down on the amount of time the runner is in use for. This will enhance user experience AND cut costs, so it's a win win.

Useful Contacts

@jhpyke

User Types

No response

Hypothesis

If we... improve linting
Then... github workflow minutes per month will decrease.

Proposal

We should only attempt to lint files users have actually changed in their PR, rather than all files in the folder. We should use files-changed as in our deployment actions, and ensure that we can specifically lint any yaml/SQL files touched by the PR on it's own. We need to validate that the action is still genuinely linting files changed, to avoid accidentally allowing bad code to be introduced.

Additional Information

No response

Definition of Done

• Action has been updated
• Linting now only triggers against files actually changed
• Linting is still effective in spotting errors in those files
• yaml and SQL linting should only trigger if changes are detected in those file types