fix: Change applicationset generate HTTP method to avoid route conflicts

[amit-o]

Closes #20757
Fixes HTTP route conflict introduced in 3a5b653
I'm not sure if PUT is the correct semantic we want here, however because /api/v1/applicationsets/{name} is already taken I wasn't sure to which route to change this to. Open to change to whatever.

If possible, would appreciate this as a hotfix to 2.13
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.29%. Comparing base (b39f3b1) to head (fb21687).
Report is 180 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20758      +/-   ##
==========================================
- Coverage   55.12%   53.29%   -1.83%     
==========================================
  Files         324      337      +13     
  Lines       55256    57055    +1799     
==========================================
- Hits        30458    30406      -52     
- Misses      22184    24012    +1828     
- Partials     2614     2637      +23     

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[amit-o]

Thanks @andrii-korotkov-verkada, is there someone we can ping for further approval?
This is a blocker for us, so I'd appreciate it if it can be hotfixed to 2.13

[andrii-korotkov-verkada]

I'll bring up the PRs marked with ready-for-review on the contributors meeting, hope they can take a look soon.

[amit-o]

Hey @andrii-korotkov-verkada, sorry for bothering, but as it's been a few contributors meetings since I'd like to ping this again

[andrii-korotkov-verkada]

I've put it as a my top item for the next meeting.

[agaudreault]

LGTM

[agaudreault]

/cherry-pick release-2.14

[agaudreault]

/cherry-pick release-2.13