Jetpack loader: prefer Jetpack loaded from customer-code

[rinatkhaziev]

Description

Previously we required the constant named WPCOM_VIP_JETPACK_LOCAL to signal the want to load from client-mu-plugins. Within the current implementation it's an extra step - because we iterate over the list of fallbacks until we find a Jetpack to load.

Changelog Description

Plugin Updated: Jetpack Loader

You don't need to set WPCOM_VIP_JETPACK_LOCAL constant in order to load Jetpack from client-mu-plugins

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

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 29.42%. Comparing base (4e19e00) to head (5a4631e).

Files	Patch %	Lines
jetpack.php	0.00%	3 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #5497      +/-   ##
=============================================
+ Coverage      29.40%   29.42%   +0.01%     
  Complexity      4759     4759              
=============================================
  Files            282      282              
  Lines          20580    20568      -12     
=============================================
  Hits            6052     6052              
+ Misses         14528    14516      -12     

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarCloud