Fix code standards and deprecations

[matthewhilton]

Changes

• Cleanup all coding standards and phpdoc warnings. Mostly done via phpcbf + manually converting unit test providers to static functions (after confirming they are truly static, just weren't labelled as such)
• Removes use of deprecated utf_encode - cherry picked commit from here Remove use of utf8_encode (deprecated in PHP 8.2) #598 - tested in S3 myself, and S3 + cloudfront in the other PR and works as expected, seems equivalent.
• Removed legacy privacy api polyfill needed because older php versions didn't support typehinting, however, Moodle 3.10 supports Php 7.2 which supports type hinting (params and return types)

To Do

• Test utf8_encode replacement and confirm it still works as expected
• Port to MOODLE_402_STABLE as well Fix codestandards 402 #622