[lldb][NFC] Fix some invalid escapes sequences in Python strings

I recently had to run the test suite with a debug Python which got started
warning about some invalid escape sequences in LLDB's Python code. They all
attempt to add a backslash by doing a single backslash instead of a double
backslash in a normal string. This seems to work fine for now, but Python says
this behaviour is deprecated, so this patch turns all those strings into raw
strings (where a single backslash is actually a single backslash)

Reviewed By: JDevlieghere

Differential Revision: https://reviews.llvm.org/D88289