fix(util): use raw strings for regex patterns (W605 invalid escapes)

[randomizedcoder]

Bug: invalid escape sequences in regex string literals (W605)

Several regex patterns in the util/ trace-analysis scripts are written as ordinary (non-raw) string literals but contain regex escapes like \[, \], \(, \), \+:

match = re.match(' *([-0-9.]+) us .* \[C([0-9]+)\]', line)   # rpcid.py, smi.py, tput.py, tthoma.py

Python treats \[ etc. as invalid escape sequences. Today they happen to evaluate to the intended backslash-plus-character, but each one emits a DeprecationWarning/SyntaxWarning and is scheduled to become a hard error in a future Python. ruff reports every one as W605.

Fix

Convert the affected literals to raw strings:

-match = re.match(' *([-0-9.]+) us .* \[C([0-9]+)\]', line)
+match = re.match(r' *([-0-9.]+) us .* \[C([0-9]+)\]', line)

Files touched: rpcid.py, smi.py, tput.py, tthoma.py, ttmerge.py, ttsyslog.py.

Every conversion is behavior-preserving. The evaluated string value is byte-for-byte identical before and after — verified by tokenizing each file and comparing ast.literal_eval of every string literal (old tree vs new tree): all values identical. One line, tthoma.py:1841, also contained a genuine \\ (backslash) escape mixed in with the invalid ones, so it becomes r'...' with the doubled backslash reduced to a single one, which keeps the exact same string value.

Verification (linter gate + regression scaffold)

Before:  ruff check --select W605 util/   ->  32 findings
After:   ruff check --select W605 util/   ->  All checks passed!  (0)

A standalone, table-driven pytest scaffold is included as executable documentation (no new CI is wired):

$ python -W error::SyntaxWarning -m pytest util/tests/test_trace_line.py -q
11 passed

util/tests/test_trace_line.py pins the trace-line regex behavior (positive / boundary / negative / corner rows, each with a description and expected) and asserts every fixed source compiles with no SyntaxWarning under warnings-as-errors — the pytest form of the W605 gate.