v1.17: ancient shrink on its own cadence (backport of #33712)

[mergify]

This is an automatic backport of pull request #33712 done by Mergify.

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[codecov]

Codecov Report

Merging #34060 (1882362) into v1.17 (353aa64) will decrease coverage by 0.1%.
The diff coverage is 0.0%.

Additional details and impacted files

@@            Coverage Diff            @@
##            v1.17   #34060     +/-   ##
=========================================
- Coverage    81.8%    81.8%   -0.1%     
=========================================
  Files         803      803             
  Lines      217915   217920      +5     
=========================================
- Hits       178391   178360     -31     
- Misses      39524    39560     +36     

[jeffwashington]

This change is minor in effect on normal validators. When a validator skips rewrites, this is a necessary and valuable change. We expect to backport a cli change to allow a validator to skip rewrites. This allows validators to opt-in testing skipping rewrites for up to months. Having this change in 1.17 adds a whole release cycle of testing.
Ancient append vec code is a no-op if we are doing rewrites (which is default). So, this change will have no effect on normal validators or rpc nodes.

[brooksprumo]

Lgtm