test: Increase Email test coverage and enable component in random tests

[gr8man]

Description
Ref: #9968

• Added additional test cases for the Email class (covering header injection prevention, SMTP disconnection handling, UTF-8 filenames, and other edge cases).
• Resolved global state pollution issues in namespace overrides by implementing cleanup in tearDown().
• Enabled the Email component in the random tests execution configuration (random-tests-config.txt).
• Fixed a PHPDoc type typo for the $newline property in Email.php.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide