[TestScript] Added Comments for the Regex Pattern in the Log Parser

Added comments for `self._regex = re.compile(f'^.*{regex_str}.*$')` in
vtr_flow/scripts/python_libs/vtr/log_parse.py.

Detailed in GitHub Issue #2743.

Author: ueqri

vtr_flow/scripts/python_libs/vtr/log_parse.py

@@ -23,6 +23,8 @@ class ParsePattern:
     def __init__(self, name, filename, regex_str, default_value=None):
         self._name = name
         self._filename = filename
+        # Look for the specified pattern somewhere in the line, but any characters
+        # can occur before and after it. Detailed in GitHub Issue #2743.
         self._regex = re.compile(f'^.*{regex_str}.*$')
         self._default_value = default_value