clp-s: Add support for escaping characters in KQL key names

[gibber9809]

Description

This PR adds support for using backslash to escape characters in KQL key names. The change is mostly contained in the StringUtiles::tokenize_column_descriptor function, but does involve a small change to the kql.g4 grammar to allow the '.' character to be escaped.

For example the key consisting of the tokens {"com.bnn", "uuid"} can now be specified as "com\.bnn.uuid" in KQL.

This PR also adds error handling for invalid KQL key names. Invalid key names currently include keys ending ending in a trailing unescaped '' or '.'.

Validation performed

• Added unit tests for parsing keys with escaped characters
• Confirmed that sensible errors are shown on the command line when entering invalid KQL queries

Summary by CodeRabbit

Summary by CodeRabbit

• New Features

  • Enhanced error handling in JSON parsing and KQL expression parsing.
  • Added support for escape sequences in column names within KQL.
  • Updated KQL grammar to recognize periods as special characters.

• Bug Fixes

  • Improved robustness of tokenization methods to prevent failures from propagating.

• Tests

  • Introduced new test cases for validating the parsing of queries with escaped characters in column names.
  • Added tests for handling illegal escape sequences in column names.