Radically simplify the generated Cargo.toml

[ivmarkov]

I think it is time to radically simplify the generated template and ask only what toolchain folks want to use:

• People routinely get confused with the embassy features -> make these mandatory in the generated Cargo.toml
• People are attempting to do no_std with esp-idf-* - which is pointless -> remove the std and alloc features from the generated Cargo.toml

[SergioGasquez]

This is a great improvement in my opinion as it really simplifies the resulting cargo.toml, which was confusing some users due to the large amount of features.