Replace ./configure with a script that generates config.toml

[ishitatsuyuki]

The rustbuild code is really bloated with code handling options from both config.mk and config.toml. We can silently replace configure with a script that generates TOML instead.

That should be possible with bash, but we can also use Python due to it's advantage like being cross platform, and a more general purpose language.

[TimNN]

Duplicate of #40730