Fix mysql2 plugin install error

[Jiannan-dev]

I've added an optional method to get the version information of the plugin. For most plugins it's not necessary to implement this method, the default require('lib/package.json') method can get its version, but the few libraries that specify export in package.json can't use default method. They must implement their own getVersion() method to get the version

Fix apache/skywalking#7879

[Jiannan-dev]

Also, for require('mysql/lib/connect') change to require('mysql').Connection also because of the restriction of the export field,The meaning of the export field can be viewed here:https://nodejs.org/dist/latest-v16.x/docs/api/packages.html

The export field of mysql2 is as follows:

"exports": {
    ".": "./index.js",
    "./promise": "./promise.js",
    "./promise.js": "./promise.js"
  }

This also means that except for require('mysql2'), require('mysql2/promise') and require('mysql2/promise.js'), all other requires are illegal, such as require('mysql2/lib/connection' ) and require('mysql2/package.json')

[Jiannan-dev]

@wu-sheng
Could help to do this pr associated to Issue:apache/skywalking#7879 ,thanks

[wu-sheng]

This should work.

[kezhenxu94]

Thank you @ruleeeer