Speed up source map VLQ encoding by removing a couple of operations from `serialize_mappings`'s hot loop.
On a local benchmark of just VLQ encoding, this change produces 5% performance increase (benchmarked on MacBook Pro M1).
In source map VLQ encoding, keep local copy of previous `Token`, rather than looking up up from `tokens`.
On a local benchmark of just VLQ encoding, this change produces 6% performance increase (benchmarked on MacBook Pro M1).
Reduce number of operations in main loop in source map VLQ encoding.
#4583 made pushing a byte to output only 2 instructions, so that makes it workable to repeat `push_byte_unchecked` inside and outside the loop.
On a local benchmark of just VLQ encoding shows this increases performance by 16% (on top of the 11% from #4583).
Probably main gain is it makes a fast path for encoding `0`, which is common.
In `oxc_sourcemap`'s VLQ encoding, avoid bounds checks when pushing bytes to the encoded string in the hot loop.
Those bounds checks are quite expensive as they involve a function call to `alloc::raw_vec::RawVec::grow_one`, and that happens on every single pushed byte.
https://godbolt.org/z/44G8jjss3
Not much difference on benchmarks, as VLQ encoding is only a small part of source map generation, but a local benchmark of just VLQ encoding shows this increases performance by 11%.
Also optimize the memory allocation in string escape. The default size in `serde_json` is 1024 for String type, we pre allocate `string.len() * 2 + 2` for every string to reduce re-allocate in escaping.
I've tried to hand write SIMD implementation, but it's too complex, so I uses the `v_jsonescape` here. But it doesn't support `aarch64` and `wasm32` simd implementation, we need to contribute to it!
Reduce memory copies when encoding source map as JSON, extending approach taken in #4476 to also avoid memory copies for source texts.
I believe reason this shows no benefit on benchmarks is because our benchmarks only create a source map from a single source file, but it should result in a speed-up when there are multiple sources.
The sourcemap implement port from
[rust-sourcemap](https://github.com/getsentry/rust-sourcemap), but has
some different with it.
- Encode sourcemap at parallel, including quote `sourceContent` and
encode token to `vlq` mappings.
- Avoid `Sourcemap` some methods overhead, like `SourceMap::tokens()`
caused extra overhead at common cases. Here using `SourceViewToken` to
instead of it.
