Release docs: Add vreplication related entries to the v20 summary

[rohit-nayak-ps]

Description

Adds VReplication section and entries to v20 summary doc.

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
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• Documentation was added or is not required

[vitess-bot]

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[mattlord]

❤️

[mattlord]

Just a side note that we should add something in the docs that includes an example usage of the flag:

--tenant-id string                   (EXPERIMENTAL: Multi-tenant migrations only) The tenant ID to use for the MoveTables workflow into a multi-tenant keyspace.

As it's not entirely clear in the flag output that this is supposed to be a column reference from the vschema. Perhaps best to just document that in the flag's help output directly.

[frouioui]

We will need to change release_notes.md on the release-20.0-rc backport

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.59%. Comparing base (bdcb43d) to head (d1a6d4f).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16259      +/-   ##
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- Coverage   68.60%   68.59%   -0.01%     
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  Files        1544     1544              
  Lines      197988   198018      +30     
==========================================
+ Hits       135825   135836      +11     
- Misses      62163    62182      +19     

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