Feature Description

Currently, CopyBytes and CopyString make a copy of the underlying data even if not required, i.e., when config.Immutable is set.
In order to improve performance, there should be a app.CopyBytes or ctx.CopyBytes which only copies the data if config.Immutable is false.

Additional Context (optional)

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Code Snippet (optional)

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Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my suggestion prior to opening this one.
• I understand that improperly formatted feature requests may be closed without explanation.