Fix help window for conda installs on Windows

[thomashampson]

Description of work

Since the dawn of the mantidworkbench conda package, attempting to open the help window in a conda install on Windows would cause the application to crash. This change fixes the issue by ensuring that the files required by Qt WebEngine (such as QtWebEngineProcess.exe, .pak resource files, and icudtl.dat) are placed alongside the conda environment’s python.exe, which is where Qt expects them.

Other approaches were tested - including providing qt.conf files and setting environment variables for the resources and QtWebEngineProcess.exe - but these had no effect. From the observed behavior, the relevant search paths appear to be hard-coded within Qt WebEngine and cannot be overridden by configuration alone.

The fix here is essentially mimicking what we do with the standalone packaging, except in that case the mantidworkbench.exe is in a more friendly location from the perspective of Qt WebEngine (inside <install_root>/bin, rather than just <env_root> as with the conda installation). The fallback search paths appear to be relative to the .exe and are:

• ../qt5/resources
• ../resources
• and the .exe location iself.

In the standalone install, because the .exe is nested inside bin, we could move the resources to ../lib/qt5. However, for the conda installation, that path would take us outside of the conda environment location because the python.exe sits in the root of the conda prefix. Taht is why we have to copy the files into the environment prefix.

Closes #34739

To test:

1. Install the Windows standalone from this build and ensure that the help window opens as expected:
   https://builds.mantidproject.org/job/build_packages_from_branch/1350/
2. Install the mantidworkbench package from conda and ensure that the help window opens as expected (previously would crash):
   mamba install -c mantid/label/windows-help-fix mantidworkbench

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Reviewer

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[thomashampson]

I have tested both the standalone install and the conda install and in both cases the help window opens as expected without error.

[thomashampson]

I'm going to merge this so that it's included in the manual testing.