fix(exporter): drop output decorators, revert migration + rename #6227

[damyanpetev]

Closes #6227
This slipped through the Angular 9 update. Migrations applied @Directive to base classes with any sort of binding and since the IgxBaseExporter had emitters decorated with @Output, ¯\(ツ)/¯, migrations must've considered it as a component base. Both decorators have been removed.

And since I semi-batch renamed classes with added Directives for lint, I'm rolling back the rename as well. I'll revert docs links if required too.

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code
• This PR includes API docs for newly added methods/properties
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes
• This PR includes behavioral changes and the feature specification has been updated with them