Wrong path for page TSconfig of backend layouts

# Bug Report

## Prerequisites

* [ ] Can you reproduce the problem on TYPO3 v11.5 LTS
* [x] Can you reproduce the problem on TYPO3 v12.4 LTS
* [x] Did you [perform a cursory search](https://github.com/issues?q=is%3Aissue+user%3Abenjaminkott+repo%3Abenjaminkott%2Fbootstrap_package)
to see if your bug or enhancement is already reported?

## Description

The import path for the page TSconfig of the backend layouts in folder [Configuration/TsConfig/Page/Mod/WebLayout/BackendLayouts](https://github.com/benjaminkott/bootstrap_package/tree/df34fd31168c4aefc034e738bd68b97bb18a19de/Configuration/TsConfig/Page/Mod/WebLayout/BackendLayouts) is wrong: **Sets/** is missing...

## Steps to Reproduce

1. Include backend layout config either via `@import` in own file or via page settings.
2. Open module "Page TSconfig"
3. Select "Included page TSconfig"
4. See error message/warning from syntax scanner like `Import does not find a file in "EXT:bootstrap_package/Configuration/TsConfig/Page/Mod/WebLayout/BackendLayouts/default.tsconfig", line number "1"`

### Expected behavior

Import should work, thus the path should be like `@import 'EXT:bootstrap_package/Configuration/Sets/BackendLayouts/PageTsConfig/BackendLayouts/default.tsconfig'`

### Actual behavior

Current import looks like `@import 'EXT:bootstrap_package/Configuration/BackendLayouts/PageTsConfig/BackendLayouts/default.tsconfig'`

## Versions

Since v15.0.2 - commit 493e840 to be more precise...

Inspect the imports under Configuration/TsConfig/Page/Mod/WebLayout/BackendLayouts and compare them with the expected Configuration/Sets/BackendLayouts/PageTsConfig/BackendLayouts path. Reproduce the issue through the Page TSconfig module and confirm that the syntax scanner no longer reports a missing file.

Written by the indexing model from the issue text.