[clang] [analyzer] Emit IssueHash in SARIF (PR #159445)

[Ziqing Luo via cfe-commits]

https://github.com/ziqingluo-90 approved this pull request.

Looks good to me.  Moving `getIssueHash` out of `HTMLDiagnostics`  is good since it is not something HTML-specific.

If I have to nitpick, I would suggest to keep the directories that are relative to the llvm repo in `hostedViewerUri`. (I guess this might not be an trivial task with `sed` though?) 

https://github.com/llvm/llvm-project/pull/159445