FormCaption - rename tokens

[thrbnhrtmnn]

Description / User Story

After changing the structure of the component tokens within #239 , we now need to adjust the token names for the FormCaption.

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Acceptance Criteria

• Design: All tokens used in the FormCaption are following the new token naming
• Dev: All tokens used in the FormCaption are following the new token naming

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Background information

• Link to new token naming documentation
• Split form.css into smaller chunks #357 should be done for this component in parallel

[larserbach]

Currently has no cmp-tokens.
Decided with @ChristianHoffmannS2 to migrate sem-token into cmp-sets.
This still needs to be done.

[larserbach]

@ChristianHoffmannS2
Token renaming is almost done. There is the following issue to resolve:
src/components/internal-components/form-caption-group/form-caption/index.ts:9:10 - error TS2305: Module '"./index.css"' has no exported member 'styleCustom'.

The error results from the change on form-caption/index.css where I migrated the css from the foundation/semantic-tokens/forms.css