refactor(elements): type base private componentRef/inject/etc access

[damyanpetev]

Updated IgxCustomNgElementStrategy access of base private props to go through typed get/set accessors so (this as any) workarounds shouldn't be needed anymore.

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 (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• 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 (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them

[github-actions]

There has been no recent activity and this PR has been marked inactive.