Help: test-parse-all-blobs

The "test-parse-all-blobs" command:

Usage: fossil test-parse-all-blobs [--limit N]

Parse all entries in the BLOB table that are believed to be non-data
artifacts and report any errors.  Run this test command on historical
repositories after making any changes to the manifest_parse()
implementation to confirm that the changes did not break anything.

If the --limit N argument is given, parse no more than N blobs