[BREAKING CHANGE] Change Atom to Atom<'a> to make it safe

[Boshen]

Part of #2295

This PR splits the Atom type into Atom<'a> and CompactString.

All the AST node strings now use Atom<'a> instead of Atom to signify it belongs to the arena.

It is now up to the user to select which form of the string to use.

This PR essentially removes this really unsafe code

oxc/crates/oxc_span/src/atom.rs

Lines 98 to 107 in 93742f8

	impl<'a> From<&'a str> for Atom {
	fn from(s: &'a str) -> Self {
	if s.len() <= INLINE_STRING_CAPACITY {
	Self(AtomImpl::Inline(InlineString::from(s)))
	} else {
	// SAFETY: It is unsafe to use this string after the allocator is dropped.
	Self(AtomImpl::Arena(unsafe { std::mem::transmute(s) }))
	}
	}
	}

which can lead to

[Boshen]

@overlookmotel Here we go ... I still remember the week it took me to understand lifetimes and adding them to the AST, which is 2 years ago. It should be faster this time ... just follow compiler errors :-)

Once the errors propagate to crates other than the ast and parser crates, I'll decide on the stop whether I want to change them to CompactString.

[codspeed-hq]

CodSpeed Performance Report

Merging #2497 will improve performances by 5.25%

_{Comparing atom-rework (9117d99) with main (93742f8)}

Summary

⚡ 1 improvements
✅ 26 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	atom-rework	Change
⚡	semantic[cal.com.tsx]	321.1 ms	305.1 ms	+5.25%