refactor(carousel): bundle styles with component

[SisIvanova]

Closes #15436
Closes #15437
Closes #15266

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

[adrianptrv]

The only difference I found is that the Carousel buttons appear above the Carousel itself. It seems that the button component styles take precedence over the .igx-carousel__arrow class.

[adrianptrv]

The $button-shadow and $indicator-active-hover-dot-color parameters from the carousel theming function don't work when included, their vars are declared but not applied to the elements. All of the other parameters work fine."

[simeonoff]

The $button-shadow and $indicator-active-hover-dot-color parameters from the carousel theming function don't work when included, their vars are declared but not applied to the elements. All of the other parameters work fine."

Do these params work in the master branch?

[adrianptrv]

The $button-shadow and $indicator-active-hover-dot-color parameters from the carousel theming function don't work when included, their vars are declared but not applied to the elements. All of the other parameters work fine."

Do these params work in the master branch?

Yes, $button-shadow work.
The $indicator-active-hover-dot-color which is set to be applied only on the "indigo" theme in the theming function, also works as expected.