🐛 bug: fix regex constraints

[efectn]

Description

It was causing regex matching problem to remove \ chars from regex constraint data for regex matchers like \\d{4}-\\d{2}-\\d{2}. To fix this, we don't remove escape chars for regex parameters. Also we no longer need to add escape chars before routing-specific characters for regex constraints.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation - https://github.com/gofiber/docs for https://docs.gofiber.io/
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I tried to make my code as fast as possible with as few allocations as possible
• For new code I have written benchmarks so that they can be analyzed and improved

Commit formatting:

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