Refine workflows

[ttytm]

What kind of change does this PR introduce?

• Codestyle
• Refactor

Did this PR introduce a breaking change?

• No

This PR contains refinements and enhancements that can be made to my recent workflow-related commits. It's things I noted down while doing DevOps work on similar GitHub actions afterwards.

result: https://github.com/tobealive/neovide/actions/runs/4275873794

Changes

• Use cache prior to clippy, as this step is sped up as well if there is a cache hit (~4min vs 30s).
• Call reusable linting workflow instead of re-authoring the linting steps in the build action. This was already intended in the original renovation, which is why workflow_call was added as part of the on block.
• Update the artifact upload condition -> Check if there is a second artifact; instead of assuming there is none on macOS and others have one.
• Update test result publishing
  • Publishing on Mac was unbearably slow due to the Python setup (should take seconds, but took ~5 min). Adding a Python setup action would improve this, but I went with abstracting the test result publishing into a workflow. This is even faster.
  • It also groups the platform results and fixes adding test results as PR comments for forks. Until now, it only worked for internal but not for PRs from forks. e.g. PR
• Require a successful build test to start the snap workflow

(Since the `Upload Test Event` and `Test Results` jobs are workflow names and will be used in the job overview on the left side of the build workflow, naming is not fully uniform. I didn't want to be too german about it and didn't update the names for the whole workflow. Please leave a word if it's preferred. I'll quickly add this small commit.)

[MultisampledNight]

Awesome, looks good to me!