Issue #1113: Add missing svg icon resolve unittest failing

[micoreyes]

To Reproduce
Steps to reproduce the behavior:

• Initiate a vanila Moodle instance in this case 4.5
• Add plugin theme_boost_union (Branch: MOODLE_405_STABLE)
• Initialize unittest
• Run vendor/bin/phpunit lib/tests/output/icon_system_fontawesome_test.php --filter test_svg_fallback
  Actual behaviour

root@1bb11dad0417:/var/www/moodle# vendor/bin/phpunit lib/tests/output/icon_system_fontawesome_test.php --filter test_svg_fallback
Moodle 4.5.8+ (Build: 20251219), 2cd8cdb7bc5df825b51ff603182fc799477e19f5
Php: 8.3.28, mysqli: 8.0.41, OS: Linux 6.8.0-47-generic x86_64
PHPUnit 9.6.18 by Sebastian Bergmann and contributors.

F                                                                   1 / 1 (100%)

Time: 00:00.246, Memory: 80.50 MB

There was 1 failure:

1) core\output\icon_system_fontawesome_test::test_svg_fallback
No SVG equivalent found for 'theme_boost_union:info'
Failed asserting that false is true.

/var/www/moodle/lib/tests/output/icon_system_fontawesome_test.php:55
/var/www/moodle/lib/phpunit/classes/advanced_testcase.php:76

FAILURES!
Tests: 1, Assertions: 519, Failures: 1.

Expected behavior

root@1bb11dad0417:/var/www/moodle# vendor/bin/phpunit lib/tests/output/icon_system_fontawesome_test.php --filter test_svg_fallback
Moodle 4.5.8+ (Build: 20251219), 2cd8cdb7bc5df825b51ff603182fc799477e19f5
Php: 8.3.28, mysqli: 8.0.41, OS: Linux 6.8.0-47-generic x86_64
PHPUnit 9.6.18 by Sebastian Bergmann and contributors.

.                                                                   1 / 1 (100%)

Time: 00:00.474, Memory: 80.50 MB

OK (1 test, 522 assertions)

Please complete the following information:

Moodle Version: 4.5.8
Boost Union Version: 2024100759