i18n Tools have PHP 7.2 compatibility issues

[Otto42]

From #40109 and related tickets, the use of create_function is being removed everywhere, so this should extend to the tools/i18n directory as well.

The makepot.php file still contains one use of create_function, while the not-gettexted.php file uses it twice.

These should be removed and replaced with alternatives.

[soulseekah]

Attached two patches that address the issue.

The first patch takes care of makepot.php, the create_function call there simply wraps the input into curly braces, so the fix is simple - move to a function of its own.

The second patch handles the two calls inside not-gettexted.php. Their usage was is a bit tricker, relying on dynamic state, so the functionality was moved into stateful classes, and a method is returned instead of a function.

The second patch also fixes two test issues in not-gettexted:

1. A failing case in the replace test: http vs https URLs in the expected result, seems like links to wordpress.org in PHP files were replaced to their secure counterparts but the po/mos were not touched, so the translation was not being found
2. construct vs setUp for initialization on the test case

All tests pass with both patches applied.

[soulseekah]

Compiled test translation changes

[ocean90]

Related: #45287

[ocean90]

The i18n tools have been removed in favour of the WP-CLI integration.