fix: Gate ignore-rule metacharacter fix behind opt-in flag [CLI-1717]

[danskmt]

Description

Provide description of this PR and changes, if linked Jira ticket doesn't cover it in full.

Checklist

• Tests added and all succeed
• Linted
• README.md updated, if user-facing

🚨After having merged, please update the snyk-ls and CLI go.mod to pull in latest client.

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[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.