backup series, fixes #7930

[ThomasWaldmann]

the archives list entries have (since ever):

• name
• timestamp
• archive_id (hex hash)

borg1:

• name is unique archive identifier on the cli (often achieved by putting a datetime at the end of the name)
• timestamp is shown in archive list (and is often redundant there due to the name)
• archive_id is also displayed in archive list, just for fun

borg2 (this PR):

• name does not need to be unique. to the contrary, users may always use the same name to identify archives belonging to the same "series" (archives resulting from backing up the same stuff at different points in time). there is no strict requirement to do it like that though, having unique archive names as in borg1 works also (they just don't belong to same series then).
• timestamp is now not redundant any more, because the name/series-identifier does not contain a datetime usually.
• archive_id is now crucial to select a specific archive, using aid:unique_archive_id_prefix because the name does not necessarily work for that anymore when using the always-same-series-name method.

aid: can be used as a pattern for the -a / --match-archives cli option to match on the archive id (prefix) instead of the archive name.

NAME positional cli argument now also supports patterns (including aid:), but requires that there is exactly ONE result from the match against the list of archives. that way, it can be used e.g. for borg extract NAME.

Some stuff got simpler by this change:

• no need to check names for uniqueness
• if series are used, the typical name-prefix match for prune we had in borg1 now becomes a precise match on the name/series-identifier.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 78.46154% with 42 lines in your changes missing coverage. Please review.

Project coverage is 81.68%. Comparing base (ae4abdf) to head (1bc5902).
Report is 11 commits behind head on master.

Files with missing lines	Patch %	Lines
src/borg/manifest.py	77.55%	12 Missing and 10 partials ⚠️
src/borg/archiver/transfer_cmd.py	64.70%	3 Missing and 3 partials ⚠️
src/borg/archive.py	85.29%	4 Missing and 1 partial ⚠️
src/borg/archiver/delete_cmd.py	64.28%	2 Missing and 3 partials ⚠️
src/borg/archiver/info_cmd.py	62.50%	1 Missing and 2 partials ⚠️
src/borg/archiver/recreate_cmd.py	91.66%	0 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8379      +/-   ##
==========================================
- Coverage   81.73%   81.68%   -0.06%     
==========================================
  Files          70       70              
  Lines       12650    12699      +49     
  Branches     2288     2300      +12     
==========================================
+ Hits        10340    10373      +33     
- Misses       1665     1671       +6     
- Partials      645      655      +10     

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