In case of most transforms (for ECMAScript), the original input source
map is used only to adjust mappings, and other fields are kept intact.

The _lazy_ variant source maps are source maps used only to call
`adjust_mappings`. It does not deserialize everything. Instead, it only
deserializes the fields required to calculate the new mappings.

This is done in the name of the performance, and the justification for
introducing a new type is at
vercel/next.js#80177 (comment)
<img width="881" alt="image"
src="https://github.com/user-attachments/assets/7ca4b084-ba46-4384-ac25-fefeae0e2513"
/>

I added some `skip_serializing_if` to `RawSourceMap`

`BytesStr` is a more efficient variant of `Arc<str>`

Since swc-project/swc#10580, SWC also uses it to store the source map strings

cherry pick #130

Co-authored-by: Sebastian Zivota <[email protected]>

A stupid typo

cherry-pick #132

---------

Co-authored-by: Sebastian Zivota <[email protected]>

Caused invalid source content:
<img width="2018" height="721" alt="image"
src="https://github.com/user-attachments/assets/dca54abd-fec5-4f4e-88ac-67e2d255dbfd"
/>