Support title and remediation text in secret detection custom rules

Problem to solve

In https://gitlab.com/gitlab-org/gitlab/-/issues/505757+s the Secret Detection Analyzer was updated to add title and remediation text from the SD rules to the gl-secrets-report.json.

These new fields, title and remediation, are not supported in custom rulesets. For example, if a customer defines the custom ruleset

title = "extension of gitlab's default gitleaks config"

[extend]
### Extends default packaged path
path = "/gitleaks.toml"

[[rules]]
title = "This is the testing title"
description = "This is the testing description"
remediation = "This is the testing remediation"
id = "testing123"
keywords = ["testing"]
regex = '''testing-key-[1-9]{3}'''

The custom rule's title and remediation fields will be ignored.

Furthermore, if a customer defines a path to extend that does not match the default gitleaks path, any title or remediation text from that file will also be ignored.

Implementation Plan

• Update analyzer to allow for title and remediation fields in custom rules - gitlab-org/security-products/analyzers/secrets!352 (merged)
• Update documentation to describe the new, optional fields - Add documentation for custom Secret Detection r... (!179796 - merged) • Craig Smith • 17.9