Add capability to limit branches by last commit date for SCM providers

[TomAdmiral]

We wanted to be able to avoid syncing stale branches and so would like to be able to do something like:

        filters:
          - repositoryMatch: dna-transform-env
          - lastCommitAge: "< 10 days"

I'm planning to write a generic plugin to do the same but we'd love this feature in the main AzureDevops provider. If it helps we might be able to submit a patch or PR for it.