Onboard new CI checks (alpha tier)

[sakanni]

Adds the alpha-tier CI workflow as part of the new CI onboarding pilot for framework repositories.

The checks run on pull requests and are non-blocking during the evaluation period. On this PR they will pass within seconds since no code changes: the first code PR after merging exercises them fully.

Details and discussion: BuroHappoldEngineering/CI_Toolkit_Proxy#13

[adecler]

This Repo is part of the installer (to be checked) so it should be in the beta tier.

[peterjamesnugent]

Test_Toolkit isn't in the installer:
https://github.com/BHoM/BHoM_Installer/blob/develop/IncludedRepos/include.txt

Agree it should probably have beta checks but I feel like in the past it has failed checks (e.g. compliance) because it is set up differently to traditional toolkits (and has a different function).

[sakanni]

Historical PRs + existing branch protection settings all characterise Test_Toolkit as an alpha marked repository i.e., only project, copyright, and serialisation checks run. New workflow only adds build (core) to the list of checks per the docs.