Field cap fix

[thalurur]

Issue #, if available:
#418

#424

Description of changes:
Update FieldCaps interception to support remote cluster indices, and also supporting both merged and unmerged response rewriting of FieldCapsResponse.

• FieldCapsResponse hold unmerged data if its a cross cluster request and merged otherwise. Earlier we were only rewriting merged data.
• Introducing a setting to stop interception in case user isn't using rollup - this acts like a kill switch if there are any unexpected behavior from the interception.

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or

(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or

(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.

(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.

[codecov]

Codecov Report

Merging #422 (66e91b0) into main (f1e59ad) will decrease coverage by 0.30%.
The diff coverage is 79.72%.

@@             Coverage Diff              @@
##               main     #422      +/-   ##
============================================
- Coverage     77.12%   76.81%   -0.31%     
+ Complexity     1550     1540      -10     
============================================
  Files           198      199       +1     
  Lines          8217     8325     +108     
  Branches       1317     1323       +6     
============================================
+ Hits           6337     6395      +58     
- Misses         1170     1230      +60     
+ Partials        710      700      -10     

Impacted Files	Coverage Δ	Complexity Δ
...xmanagement/rollup/actionfilter/FieldCapsFilter.kt	46.54% <62.29%> (-29.20%)	21.00 <14.00> (-7.00)
...ticsearch/indexmanagement/IndexManagementPlugin.kt	89.13% <62.50%> (-3.62%)	12.00 <2.00> (+1.00)	⬇️
...indexmanagement/rollup/actionfilter/SerDeHelper.kt	98.48% <98.48%> (ø)	0.00 <0.00> (?)
.../indexmanagement/rollup/settings/RollupSettings.kt	97.56% <100.00%> (+0.33%)	1.00 <0.00> (ø)
...nt/indexstatemanagement/model/destination/Slack.kt	40.90% <0.00%> (-13.64%)	2.00% <0.00%> (-2.00%)
...indexmanagement/rollup/model/RollupFieldMapping.kt	75.00% <0.00%> (-8.34%)	6.00% <0.00%> (-1.00%)
...nt/rollup/action/stop/TransportStopRollupAction.kt	65.30% <0.00%> (-2.05%)	8.00% <0.00%> (ø%)
...ndexstatemanagement/IndexStateManagementHistory.kt	78.26% <0.00%> (-1.74%)	26.00% <0.00%> (-1.00%)
...csearch/indexmanagement/rollup/util/RollupUtils.kt	79.25% <0.00%> (-1.25%)	0.00% <0.00%> (ø%)
... and 3 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f1e59ad...66e91b0. Read the comment docs.

[dbbaughe]

nit: Can we split these into individual files with filenames as their classnames?

[thalurur]

In this case I think its better to contain these classes in a single file to keep the code contained at one place.