Address PHPCS errors

[vikrampm1]

The extension has the standard Woo PHPCS ruleset set up as a GitHub Action to check changed lines on PRs, but running PHPCS across all files of the repo is failing on the trunk branch. A total of 412 errors and 154 warnings were found in 99 files (PHPCS errors/warnings log, summary). This aims to resolve the errors in batches by file directories, but limit updates on the warnings to as those files are touched by future extension PRs. First to address any security-related errors and then use the PR check to gradually improve the non-security errors over time.