refactor(sbb-tab): align with sbb-stepper

[DavideMininni-Fincons]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the pull request tracker for a Pull Request (PR) that matches the one I want to submit, without success.

Issue

This PR Closes #2240 #1351

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

See Review Guidelines for more information what is checked during review process.

Changes

Changes in this pull request:

• the sbb-tab-title has been renamed sbb-tab-label to align the naming with the stepper;
• a new component named sbb-tab has been added; the content of a single tab within the tab group must be included in this new component (article, section and div are not supported anymore);
• the sbb-tab has the logic to retrieve the related label
• the didChange event now emits an object which contains the current (and previous, if available) tab index, tab label and tab content.

Browsers

I tested the build on the following browsers:

• Firefox Desktop
• Chrome Desktop
• Edge Desktop
• Safari Desktop
• Chrome Mobile
• Safari Mobile

Screen readers

I tested the build on the following browsers:

• JAWS Firefox Desktop
• JAWS Chrome Desktop
• NVDA Firefox Desktop
• NVDA Chrome Desktop
• VoiceOver Safari Desktop
• VoiceOver Chrome Desktop
• VoiceOver Safari Mobile
• Android Accessibility Suite Chrome Mobile

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Does this introduce a breaking change?

• Yes
• No

BREAKING CHANGE

• the sbb-tab-title has been renamed to sbb-tab-label;
• the only supported tag for the tab content is the newly created sbb-tab; article, section and div are not supported anymore;
• the didChange event on sbb-tab-group now includes an object which contains the currently selected tab index, sbb-tab-label and sbb-tab, and, if available, the previous ones.

Other information

[jeripeierSBB]

Nice work so far! I think also in terms of implementation there could be improvements to the previous version, but you covered the breaking changes, so probably for now it's should be ok :-).

[jeripeierSBB]

LGTM, thank you