[TASK] Use <template> for document fragments in form editor

The `script` tag is defined to hold executable code or data and
not template html markup. We are switching this to the `template`
tag that is indended for this usecase.

Resolves: #101769
Releases: main, 12.4
Change-Id: I0657e5cbce7e13770ce88918cb9e4137bf017590
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80681


Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>