Use stable instead of nightly

[PopcornPaws]

Description

Since this PR has successfully been merged, it's just a matter of time that it will end up in the latest release. We should try to bump our dependencies to match that latest version and switch to stable rust instead of nightly.

Side note: only the wasm runtime builder needed nightly up to this point

Solution

• test that everything builds as intended using stable rust
• update docs to use stable instead of nightly (wasm target as well)
• remove rust-toolchain.toml
• dockerfiles should be updated accordingly (no need for the nightly image)
• ci/cd pipeline