ci: Be more specific when to run the main Unit checks

[ac000]

ci-dev-distro-compiler.yaml already limits itself to running only when relevant things are updated.

[danielledeleo]

Can we exclude Markdown changes too?

[ac000]

For ci-dev-distro-compiler.yaml I do

    paths:
      - configure
      - 'auto/**'
      - 'src/**'
      - 'test/**'
      - '.github/workflows/ci-dev-distro-compiler.yaml'

I can basically do that here...

[ac000]

Specify when to run as opposed when not to...

$ git range-diff c40ca24d...d27133c9
1:  c40ca24d ! 1:  d27133c9 ci: Don't run main Unit checks on changes to tools/
    @@ Metadata
     Author: Andrew Clayton <a.clayton@nginx.com>

      ## Commit message ##
    -    ci: Don't run main Unit checks on changes to tools/
    -
    -    Also ignore changes to unitctl.yml
    +    ci: Be more specific when to run the main Unit checks

         ci-dev-distro-compiler.yaml already limits itself to running only when
         relevant things are updated.
    @@ .github/workflows/ci.yml: name: ci
     -    branches:
     -      - master
     +    branches: master
    -+    paths-ignore:
    -+      - 'tools/**'
    -+      - '.github/workflows/unitctl.yml'
    ++    paths:
    ++      - configure
    ++      - 'auto/**'
    ++      - 'go/**'
    ++      - 'src/**'
    ++      - 'test/**'
    ++      - '.github/workflows/ci.yml'

      jobs:
        test:

[ac000]

Rebased with master..