Hexview feature parity

[DubiousDoggo]

Description

• QHexDocument reads directly from the VGMFile
• Moved some functionality from QHexDocument and QHexCursor into QHexView
• Selected events in the tree view are highlighted in the hexview, bold with red outline, and visa versa
• Updated font

How Has This Been Tested?

• General UI stress testing

Screenshots:

• Container selection from tree view
  

• Multi line selection
  

• Contiguous Area
  

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• I have read the CONTRIBUTING document.

[sykhro]

Looks very good overall, please remember to squash the fixup commits.

[sykhro]

The changes are fine but they should be squashed onto their original commits (commit message says "remove dead code" but actually does a whole lot more).