Authentication configuration fields do not handle escape sequences (\H) correctly

Summary

A customer scan fails with an error similar to: ERR MAIN configuration validation failed error="failed to parse TOML configuration due to (16, 13): invalid escape sequence: \\H"

This is due to the \ character not being escaped. We should escape all \ characters prior to inserting into the browserker.toml configuration file.

How to reproduce:

Set any DAST variable that is used in generating the Browserker configuration to a string containing an invalid sequence: DAST_PASSWORD: "pass\Hword"