instead of passing rustflags internally, simply add a .cargo/config.toml entry with alternative profiles

[jkelleyrtp]

Feature Request

Cross platform builds are hard!!

Currently wasm / fullstack are quite slow if their dependencies are not properly optimized up to a higher opt level and some debug info is stripped.

We do this internally by using cargo rustc to build things but those flags are not exposed and not easy to disable.

In reality, we should simply add extra profiles to the config.toml, or just override the dev and release profiles automatically.

This would fix a number of issues with duplicate full recompiles since we're no longer busting the cache between first build, rust-analyzer build, and asset collection.

This would also let us circumvent configuration issues for faster checks:
#2523
#1796