🩹[Fix]: Added respects body immutability to ctx.Body() and ctx.BodyRaw() functions.

[asyslinux]

Description

Added respects body immutability to ctx.Body() and ctx.BodyRaw() functions.

Related to #2757

Changes Introduced

• Benchmarks: go test -run Test_Ctx_Body -bench=Benchmark_Ctx_Body -benchmem
• Documentation Update: documentation already has full information and comments about body immutability.

Type of Change

• Enhancement (improvement to existing features and functionality)

Checklist

Before you submit your pull request, please make sure you meet these requirements:

• Followed the inspiration of the Express.js framework for new functionalities, making them similar in usage.
• Conducted a self-review of the code and provided comments for complex or critical parts.
• Updated the documentation: documentation already has full information and comments about body immutability.
• Added or updated unit tests to validate the effectiveness of the changes or new features.
• Ensured that new and existing unit tests pass locally with the changes.
• Verified that any new dependencies are essential and have been agreed upon by the maintainers/community.
• Aimed for optimal performance with minimal allocations in the new code.
• Provided benchmarks for the new code to analyze and improve upon.

[efectn]

Can't we add a new methods like copyString like we did it getString or getBytes?

[asyslinux]

Can't we add a new methods like copyString like we did it getString or getBytes?

@efectn, Please read a issue: #2757 (comment)
We with @ReneWerner87 choose to use simple if, because body sometimes can be large and use func []byte []byte is not optimal in this case, simple if is cheaper. I checked via GodBolt, and compiler not inline this function by default, then call to function is more expensive then simple if, and also state of variable c.app.config.Immutable is unknown within compile-time.

[ReneWerner87]

LGTM