feat(data_structures): add CodeBuffer::*_unchecked_cap methods

[overlookmotel]

Add 3 methods to CodeBuffer:

• print_byte_unchecked_cap
• print_bytes_unchecked_cap
• print_str_unchecked_cap

All 3 are unsafe methods which require caller to ensure there is sufficient capacity in the buffer. This allows minimizing bounds checks when pushing multiple bytes sequences to the buffer.

let mut buf = CodeBuffer::new();

let s: &str = "Hello, ";
let b: &[u8] = b"world";
let c: u8 = b'!';

buf.reserve(s.len() + b.len() + 1);

// No bounds checks.
// SAFETY: Have reserved sufficient capacity
unsafe {
    buf.print_str_unchecked_cap(s);
    buf.print_bytes_unchecked_cap(b);
    buf.print_byte_unchecked_cap(c);
}

[overlookmotel]

• feat(data_structures): add CodeBuffer::*_unchecked_cap methods #10075 👈 (View in Graphite)
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #10075 will not alter performance

_{Comparing 03-27-feat_data_structures_add_codebuffer__unchecked_cap_methods (d53e323) with main (5e14fe9)}

Summary

✅ 33 untouched benchmarks

[overlookmotel]

I wrote these originally to use in #10046, but turns out they're unnecessary there. But these are still useful APIs, so I think worthwhile adding them.

[Boshen]

I'm not keen to add code that's never going to be used though. Do we have scenarios for these 3 methods?