Tests + Fix for non-empty string storageID tierFS

[nadavsteindler]

Debt from the StorageID tierFS issue. As per Ariel's comment:
#8549 (review)

On the dev side, I am unable to find anywhere that tests a non-empty storage ID. This might be worrying? (This request is blocking: we should test non-empty storage IDs, or state on the description of this PR why the existing tests are sufficient, or keep the issue open until we do have a PR that tests it.)

Note the comment in the design: the StorageID will currently only be allowed to be empty/nil.

What levels should we test at?

• TierFS- this is the lowest level change and interesting stuff happens at this layer. Add tests
• committed manager- we will significantly change & test it as part of Range and Metarange per StorageID #8595
• Catalog- didn't significantly change(yet)

[arielshaqed]

I understand that this issue is to test TierFS with nondefault StorageIDs. This is really important! Please note that #8549 is actually broader than its title makes it sound; in addition to TierFS, it adds StorageIDs to at least:

• Catalog
• Committed data
  • including import
  • Commits and merges
• Range and metarange managers and writers

All this plumbing has to work, so we will have to test it. By deciding to pass StorageID as a parameter rather than on a context or on objects, we pretty much committed to testing all those parameters.

[nadavsteindler]

I understand that this issue is to test TierFS with nondefault StorageIDs. This is really important! Please note that #8549 is actually broader than its title makes it sound; in addition to TierFS, it adds StorageIDs to at least:

• Catalog

• Committed data

  • including import
  • Commits and merges

• Range and metarange managers and writers

All this plumbing has to work, so we will have to test it. By deciding to pass StorageID as a parameter rather than on a context or on objects, we pretty much committed to testing all those parameters.

Sorry I didn't write out all my thoughts. I want to also test CommitedManager and Catalog BUT Catalog didn't significantly change yet in that PR and CommittedData will change in the Ranges & Metaranges PR so I will write those tests there