Release file: support Version field

[xzhang1]

https://wiki.debian.org/DebianRepository/Format#Version

The Version field, if specified, shall be the version of the release. On the other hand, if not set or set to an empty value, the Version field will not be included in the Release file.

Fixes # 1495

Requirements

All new code should be covered with tests, documentation should be updated. CI should pass.

Also, to speed up things, if you could kindly "Allow edits and access to secrets by maintainers" in the
PR settings, as this allows us to rebase the PR on master, fix conflicts, run coverage and help with
implementing code and tests.

Description of the Change

Add parameter "version" to the commands "publish repo/snapshot", "publish update", and "publish switch".
Add parameter "version" to below REST API:

• Publish Snapshot/Local Repo
• Update Published Local Repo/Switch Published Snapshot

If "version" is not set or set to empty string, no "Version" domain in Rlease file.

Modify test cases:

• PublishSnapshot24Test
• PublishSwitch17Test
• PublishUpdate20Test
• PublishUpdateAPITestRepo
• PublishSwitchAPITestRepo

New added test cases:

• PublishRepo36Test
• PublishUpdate21Test

Checklist

• allow Maintainers to edit PR (rebase, run coverage, help with tests, ...)
• unit-test added (if change is algorithm)
• functional test added/updated (if change is functional)
• man page updated (if applicable)
• bash completion updated (if applicable)
• documentation updated
• author name in AUTHORS

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.67%. Comparing base (a65f79e) to head (ed28e12).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1533      +/-   ##
==========================================
- Coverage   76.96%   76.67%   -0.29%     
==========================================
  Files         160      160              
  Lines       14754    14775      +21     
==========================================
- Hits        11355    11329      -26     
- Misses       2266     2317      +51     
+ Partials     1133     1129       -4     

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