[BUGFIX] Do not render nonceProxy if nonce has not been consumed

Allow proxies to cache the TYPO3 content by stripping the nonce from
the generated CSP header if the nonce was not actually consumed.

Also ensure that the nonce value substitution consumes a nonce
to ensure that a (replaced) nonces in cached-content receive
a matching CSP header as well.

Resolves: #103942
Releases: main, 12.4
Change-Id: I437c83de522ff4a6f4ee0ef2f13881d24bfb990c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84435


Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Kai Ole Hartwig <o.hartwig@moselwal.de>
Tested-by: Willi Wehmeier <wwwehmeier@gmail.com>
Reviewed-by: Willi Wehmeier <wwwehmeier@gmail.com>