Deprecate wpcom_vip_term_exists()

[rebeccahum]

Description

Going to break #4983 up. Let's start with wpcom_vip_term_exists() because 99.9% is on WP 6.0+

Changelog Description

Function Updated: wpcom_vip_term_exists

Deprecate wpcom_vip_term_exists() because WP 6.0 now has caching in term_exists(). Please use core function instead.

Pre-review checklist

Please make sure the items below have been covered before requesting a review:

• This change works and has been tested locally (or has an appropriate fallback).
• This change works and has been tested on a Go sandbox.
• This change has relevant unit tests (if applicable).
• This change uses a rollout method to ease with deployment (if applicable - especially for large scale actions that require writes).
• This change has relevant documentation additions / updates (if applicable).
• I've created a changelog description that aligns with the provided examples.

Pre-deploy checklist

• VIP staff: Ensure any alerts added/updated conform to internal standards (see internal documentation).

Steps to Test

[sonarqubecloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (b4dad7f) 28.88% compared to head (a1588d9) 28.84%.

Files	Patch %	Lines
vip-helpers/vip-deprecated.php	0.00%	3 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #5100      +/-   ##
=============================================
- Coverage      28.88%   28.84%   -0.05%     
  Complexity      4767     4767              
=============================================
  Files            279      279              
  Lines          21012    20983      -29     
=============================================
- Hits            6070     6052      -18     
+ Misses         14942    14931      -11     

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