autodiscoverProjects for Bitbucket Cloud

[rarkins]

Describe the proposed change(s).

Discussed in #27093

I think it's best to make this a new option because, apart from it being a different name (projects vs namespaces), Bitbucket Cloud also has these differences vs GitLab:

• Filtering would be done client-side not server-side
• Ability to use patterns and/or excludes

So we should create a new option autodiscoverProjects, for Bitbucket Cloud only, and use the matchRegexOrGlobList() function which allows exclusions.

[viceice]

can this be faked with our topic filter?

[rarkins]

I think they're potentially too different semantics