Add memory-safety guideline

[salticecream]

This PR adds a new guideline, memory-safety, which can be useful for developers who are interested in catching specifically memory-safety bugs.

Furthermore, my suggestion (included in the PR) is to raise unix.MismatchedDeallocator and unix.Malloc to HIGH severity. The former always leads to UB on true positives, and the latter almost always.

[bruntib]

Please, extend this list accordingly:

codechecker/web/server/vue-cli/src/components/Statistics/Guideline/GuidelineStatistics.vue

Line 177 in 834807d

const guidelineOptions = [

Also, add the new list item to the selected items' list:

codechecker/web/server/vue-cli/src/components/Statistics/Guideline/GuidelineStatistics.vue

Line 211 in 834807d

selectedGuidelineIndexes: [ 0, 1, 2, 3 ],

Yes, you're right, this should be added dynamically in the future :)

Also, the severity of some checkers are changed (from medium to high, for example). This breaks some tests: https://github.com/Ericsson/codechecker/actions/runs/17100480035/job/48495383987?pr=4654
I would say that severity change of such important checkers should be done in an independent pull request if we decide to change them.

Thank you!

[dkrupp]

LGTM