Wasm httplib replacement2

[carlopi]

This improves the codepath for problematic cases where JavaScript request would fail / throw.

There is a change outside of Wasm: using HTTPException instead of std::runtime_error.
They should behave about the same (since HTTPException is a std::runtime_error), but be rendered somehow better.

Error message in case of CORS errors is now:

SELECT load_macro_from_url('https://gist.github.com/lmangani/518215a68e674ac662537d518799b893/raw/5f305480fdd7468f4ecda3686011bab8e8e711bf/bsky.sql') as res;
HTTP Error: 400: Unknown error, something went quack in Wasm land! Please consult the console and or the docs at https://duckdb.org/community_extensions/extensions/webmacro