Add support for Qualcomm Hexagon processor

[aleksxtrfy]

This PR adds initial support for the Qualcomm Hexagon (QDSP6) processor
to Ghidra. It includes Sleigh language definitions and basic tests.

Changes:

• Added Ghidra/Processors/HEXAGON with Hexagon language files
• Updated build configuration to include Hexagon
• Added sample binaries and tests

Resolves #8741

[CUB3D]

Hi, this appears to be an older fork of my own plugin (https://github.com/CUB3D/ghidra-hexagon-sleigh), with the test cases and the original License removed. I'm not exactly happy that this has been put here without asking me first, but I'd be happy to collaborate and get an up to date version of this merged if the Ghidra team is interested. I'd either need to get the approval of other contributors or (preferably) have this integrated as part of the GPL components of Ghidra. It's also worth adding that this is not yet complete and needs more testing e.g. It's missing large portions of HVX

[jobermayr]

@CUB3D: This PR isn't buildable. Inspired by this PR I took files from your repo to create a buildable patch (I would be happy if you take it (put you as author for my changes) and manage your own PR):
https://github.com/jobermayr/ghidra-staging/blob/master/8782-Add-support-for-Qualcomm-Hexagon-processor.patch