If a resource references a source map (or if we find a source map based
on the resource name + ".map"):
1. Use that source map for the debug variant of the resource
2. Pass it to terser so it can update it based on the transformation,
   preserving the mapping to the initial source

…le path

We expect source maps to be referenced in the respective source

…e been modified in previous tasks

* Always remove existing source map references from resource. Re-add
  reference to debug variant under certain conditions.
* Add tests

…urce map entries

This solves an issue where clicking on a line of generated bundle
content in the dev tools still openes the module located above the
expected one. We must always ensure that the first column is mapped.

Currently only fails because default of "useInputSourceMaps" option
of minify task is set to "false".

Co-authored-by: Günter Klatt <57760635+KlattG@users.noreply.github.com>

* Move integration tests into speparate file
* Also tag the sourcemap associated with the debug resource as
  "IsDebugVariant"