[TASK] Enable direct access to nested settings properties in fluid

Implement ContainerInterface in order for fluid[1] to be able
to access settings properties directly, instead of using
`{settings.all.property}`, e.g. when accessing site settings
directly via `{site.settings.mysite.brandColor}`.

[1] https://github.com/TYPO3/Fluid/issues/1001 (raised in #104896)

Releases: main
Related: #104858
Related: #104896
Resolves: #104906
Change-Id: Ia6cd703dfc2faca5f6324174ee343610cc32a6b3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/86013


Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>