[check-codeowners.sh] Validate entries in ALLOWLIST are not owned

[mx-psi]

The .github/scripts/check-codeowners.sh script is useful to validate that components have an owner by checking that all entries on CODEOWNERS are valid and are not in the ALLOWLIST file.

It would be useful to also validate that the ALLOWLIST file does not have any entries that actually have an owner, so that it accurately reflects the orphaned components.

[Chinwendu20]

Hello @mx-psi @TylerHelmuth . Could I please work on this?

[mx-psi]

Assigned to you @Chinwendu20

[Chinwendu20]

Thanks for assigning this to me @mx-psi. So I plan on creating a function for this. Would it be okay if I put this in a separate file or this should be in the check-codeowners.sh file?

[Chinwendu20]

Update, I am ready to push a PR just want to confirm the above, first.

[mx-psi]

@Chinwendu20 Either way works for me, just open the PR with whatever you have and we will resolve this on the PR :)

[Chinwendu20]

Thanks @mx-psi. I have pushed it. I am unsure if this requires a changelog.