hexagon: add support for linux on snapdragon (#21707)
* hexagon: add support for debian on ex2
* hexagon: add -fvectotize to c/c++ cmake flags
* hexagon: remove trailing white space
* update onboarding steps
* hexagon: update linux setup documentation
* hexagon: update intallation scripts
* Hexagon: update docs
* hexagon: update onboarding scripts
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Co-authored-by: Zack Li <zackli@qti.qualcomm.com>
