[SECURITY] Prohibit TypoScript in form yaml files

Only evaluate TypoScript-like instructions like

```
submitButtonLabel = TEXT
submitButtonLabel.value = Bar
```

defined within

`plugin.tx_form.settings.formDefinitionOverrides`
and
`plugin.tx_form.settings.yamlSettingsOverrides`

and **not** within form definition yaml files or
the form setup yaml files.

This is achieved by not searching the entire form
definition or form setup for TypoScript instructions,
but only the actual TypoScript.

Resolves: #98403
Releases: main, 11.5, 10.4
Change-Id: I7b066f109d6061715c2240b01ed15185c58fa9f5
Security-Bulletin: TYPO3-CORE-SA-2022-015
Security-References: CVE-2022-23503
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77092


Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>