Restructure compatibility testing workflow to depend on stable job

[MrAlias]

Currently the compatibility CI testing defined with the version of Go it is testing against in its name.

opentelemetry-go/.github/workflows/ci.yml

Lines 115 to 152 in 69d0946

	compatibility-test:
	strategy:
	matrix:
	go-version: ["1.20", 1.19, 1.18]
	os: [ubuntu-latest, macos-latest, windows-latest]
	# GitHub Actions does not support arm* architectures on default
	# runners. It is possible to acomplish this with a self-hosted runner
	# if we want to add this in the future:
	# https://docs.github.com/en/actions/hosting-your-own-runners/using-self-hosted-runners-in-a-workflow
	arch: ["386", amd64]
	exclude:
	# Not a supported Go OS/architecture.
	- os: macos-latest
	arch: "386"
	runs-on: ${{ matrix.os }}
	steps:
	- name: Install Go
	uses: actions/setup-go@v3
	with:
	go-version: ${{ matrix.go-version }}
	- name: Checkout code
	uses: actions/checkout@v3
	- name: Setup Environment
	run: |
	echo "GOPATH=$(go env GOPATH)" >> $GITHUB_ENV
	echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
	shell: bash
	- name: Module cache
	uses: actions/cache@v3
	env:
	cache-name: go-mod-cache
	with:
	path: ~/go/pkg/mod
	key: ${{ runner.os }}-${{ env.cache-name }}-${{ hashFiles('**/go.sum') }}
	- name: Run tests
	env:
	GOARCH: ${{ matrix.arch }}
	run: make test-short

This is needed to clearly identify what is being testing in the job.

However, our PRs are setup to require these jobs to pass and when we bump our supported Go versions we then need to request community access to update this requirement.

Instead, we could use the needs directive for a token job that follows all the compatibility testing jobs and require that job to succeed. That way if any of the compatibility tests fail the token job will also fail but the token job will remain "stable" from the perspectives of PR required checks.