Improve tests, asserions, CI setting and etc

[peter279k]

Changed log

• Fix Psalm analysis error
• Removing some comment annotations because they're unused.
• Adding the pull_request trigger to let upcoming PR can do GitHub Action work automatically.
• Fixing the AnnotationTest class namespace.
• Using the assertCount to assert expected count is same as result.
• To fix following Composer error, using the php-7.2 version to update cached dependencies:

Your lock file does not contain a compatible set of packages. Please run composer update.

  Problem 1
    - ocramius/package-versions is locked to version 1.4.2 and an update of this package was not requested.
    - ocramius/package-versions 1.4.2 requires composer-plugin-api ^1.0.0 -> found composer-plugin-api[2.0.0] but it does not match the constraint.
  Problem 2
    - ocramius/package-versions 1.4.2 requires composer-plugin-api ^1.0.0 -> found composer-plugin-api[2.0.0] but it does not match the constraint.
    - vimeo/psalm 3.12.1 requires ocramius/package-versions ^1.2 -> satisfiable by ocramius/package-versions[1.4.2].
    - vimeo/psalm is locked to version 3.12.1 and an update of this package was not requested.

ocramius/package-versions only provides support for Composer 2 in 1.8+, which requires PHP 7.4.
If you can not upgrade PHP you can require composer/package-versions-deprecated to resolve this with PHP 7.0+.