[lldb] Tidy some regex in crashlog.py (NFC)

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