A spiritual follow up to D131032. I noticed some regex could be simplified.

This does some of the following:
1. Removes unused capture groups
2. Uses non-capturing `(?:...)` groups where grouping is needed but capturing isn't
3. Removes trailing `.*`
4. Uses `\d` over `[0-9]`
5. Uses raw strings
6. Uses `{N,}` to indicate N-or-more

Also improves the call site of a `re.findall`.

Differential Revision: https://reviews.llvm.org/D131305

Add a parser for JSON crashlogs. The CrashLogParser now defers to either
the JSONCrashLogParser or the TextCrashLogParser. It first tries to
interpret the input as JSON, and if that fails falling back to the
textual parser.

Differential revision: https://reviews.llvm.org/D91130