Substitute variables in path names of template repos too (#25294)

### Summary

Extend the template variable substitution to replace file paths. This
can be helpful for setting up log files & directories that should match
the repository name.

### PR Changes

 - Move files matching glob pattern when setting up repos from template
- For security, added ~escaping~ sanitization for cross-platform support
and to prevent directory traversal (thanks @silverwind for the
reference)
 - Added unit testing for escaping function 
- Fixed the integration tests for repo template generation by passing
the repo_template_id
- Updated the integration testfiles to add some variable substitution &
assert the outputs

I had to fix the existing repo template integration test and extend it
to add a check for variable substitutions.

Example:

![image](https://github.com/go-gitea/gitea/assets/12700993/621feb09-0ef3-460e-afa8-da74cd84fa4e)

doc/usage/template-repositories.en-us.md

@@ -51,6 +51,8 @@ a/b/c/d.json
 
 In any file matched by the above globs, certain variables will be expanded.
 
+Matching filenames and paths can also be expanded, and are conservatively sanitized to support cross-platform filesystems.
+
 All variables must be of the form `$VAR` or `${VAR}`. To escape an expansion, use a double `$$`, such as `$$VAR` or `$${VAR}`
 
 | Variable             | Expands To                                          | Transformable |