Blobstore can throw FileAlreadyExistsException #10447

[rymsha]

• catche FileAlreadyExistsException, to allow NodeVersions with the same blob-keys to be created in parallel.
• CachedBlobStore refactored to minimize memory impact of not cached records
• verify integrity of blobs to be cached - by checking blobkey corresponds with blob content.
• because cache is shared between repositories, cache invalidation on blob deletion is removed
• NodeVersionService refactored to report exact failed blob load

Additionaly flob file last-modified update removed to avoid concurrent file writes entirely. Blob last-modified has no big value anyway and may be harmful.

• last-modified change does not work on smbfs
• CachedBlob shades real filesystem value with a randomly chosen one (cache shares blobs between repositories)
• Vacuum is the only user of last-modified value but is is nearly useless Do not remove blob of non-transient repositories during vacuum #10794

[codecov]

Codecov Report

Attention: Patch coverage is 83.56164% with 12 lines in your changes missing coverage. Please review.

Project coverage is 84.51%. Comparing base (f71fde8) to head (f592349).
Report is 15 commits behind head on 7.15.

Files with missing lines	Patch %	Lines
...c/xp/internal/blobstore/cache/CachedBlobStore.java	76.00%	5 Missing and 1 partial ⚠️
.../xp/repo/impl/node/dao/NodeVersionServiceImpl.java	89.74%	3 Missing and 1 partial ⚠️
...onic/xp/internal/blobstore/file/FileBlobStore.java	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               7.15   #10831   +/-   ##
=========================================
  Coverage     84.51%   84.51%           
+ Complexity    19629    19623    -6     
=========================================
  Files          2608     2607    -1     
  Lines         68292    68288    -4     
  Branches       5435     5436    +1     
=========================================
- Hits          57718    57715    -3     
+ Misses         7937     7934    -3     
- Partials       2637     2639    +2     

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