Refactor "applyLocale" and remove references to "language" column in UFMatch table

[christianwach]

Overview

Fixes issues raised in this ticket on Lab.

Before

• CRM_Core_BAO_ConfigSetting::applyLocale() does not apply the desired locale when inheritLocale is specified.
• CRM_Core_BAO_ConfigSetting::applyLocale() reads and saves the locale in the UFMatch table with no discernible use case in doing so.
• CRM_Admin_Form_Setting_Localization::onChangeLcMessages() saves the locale in the UFMatch table for the contact/user that saves the setting, again with no discernible effect.

After

• CRM_Core_BAO_ConfigSetting::applyLocale() correctly applies the desired locale when inheritLocale is specified.
• CRM_Core_BAO_ConfigSetting::applyLocale() and CRM_Admin_Form_Setting_Localization::onChangeLcMessages() no longer touch the language column in the UFMatch table.

Technical Details

See this ticket on Lab for full discussion.

tl;dr This PR fixes a regression where CRM_Core_BAO_ConfigSetting::applyLocale() no longer applies the desired locale when inheritLocale is specified and removes references to the seemingly-unused language column in the UFMatch table.

Comments

• I don't know how to create the upgrade script to remove the column from the table itself.
• I'm not sure how to write tests for this.

[civibot]

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[mattwire]

I think we can leave the upgrader step for a later version of CiviCRM - in case there are any wierd and wonderful customisations that still use it they won't break immediately (or at least won't lose the data).

[christianwach]

@mattwire Ah yes, good point!

[eileenmcnaughton]

@mattwire @mlutfy @seamuslee001 we talked about getting this merged before the next rc is cut - does anyone feel comfortable enough with this to merge?

[mattwire]

Yes, I'm happy with this. I've got it running on a couple of sites. Anyone using multiple languages should do a little extra testing on 5.29 to check everything works ok @kcristiano @aydun @MikeyMJCO @mlutfy