It caused the final executable to grow by 1.5 mb, and is not having any
other benefit.

This reverts commit 2b40fa06.

Instead of using core/snapshot_creator.rs, instead two crates are
introduced which allow building the snapshot during build.rs.

Rollup is removed and replaced with our own bundler. This removes
the Node build dependency. Modules in //js now use Deno-style imports
with file extensions, rather than Node style extensionless imports.

This improves incremental build time when changes are made to //js files
by about 40 seconds.

So that "cargo build" will build it when the gn frontend is eventually
removed.

A lot of its functionality is unused still, but the goal it to slowly
migrate logging functionality to it. There is also a useful progress bar
which can be ported over later - it depends on this module.

https://github.com/rust-lang/cargo/blob/4c1fa54d10f58d69ac9ff55be68e1b1c25ecb816/src/cargo/util/progress.rs