Support the TOML config file format for Rust launch configurations

[scottyancey]

We have support for .env files in launch configurations via the envFile parameter.

It would be great to add support for .toml files considering TOML config files are Rust standard.

For example, developers would have two options to pass in config information to launch targets. So in addition to what exists today:

envFile: "<path_to_env_file>"

We'd also have a choice to use this:

configTomlFile: "<path_to_config_toml_file>"

This was originally filed as a bug, but I agree it's not a bug it's a feature request. Hence filing this here!