Versioning: don't wait for indexer before refresh

[mbien]

indexing and versioning status updates can run concurrently since they don't interact with each other.

git status refresh typically takes < 1s even in large projects, while indexing can take much longer.

expected results:

• you should see the git file status update long before indexing finishes. for example while switching between branches on larger projects or right after NB startup
• no noteworthy regressions for indexing totals or other tasks

draft; just for testing. Enable with -J-Dversioning.delayscan.disable=true