Opt out from default derives and attributes

[pmikolajczyk41]

This PR aims at giving the subxt user full control over derived traits and attributes for generated types. Until now, every new type was given:

#[derive(
    #crate_path::ext::scale_encode::EncodeAsType,
    #crate_path::ext::scale_decode::DecodeAsType,
    #crate_path::ext::codec::Encode,
    #crate_path::ext::codec::Decode,
    Debug
)]
#[encode_as_type(crate_path = #encode_crate_path)]
#[decode_as_type(crate_path = #decode_crate_path)]
#[codec(crate = #crate_path::ext::codec)]

This in particular meant that subxt was assumed to be available when working with just subxt_macro crate. In order to allow some flexibility, we add (both to the macro and CLI):

• option to opt out from these defaults
• arguments to provide both universal (for every type) and type-specific derives and attributes

[jsdw]

A couple more naming nits for consistency with DerivesForType etc but otherwise looks great!

[pepoviola]

Suggested change

	/// Example `--attribute-type my_module::my_type=#[allow(clippy::all)]`.
	/// Example `--attributes-for-type my_module::my_type=#[allow(clippy::all)]`.

Typo on docs.

[jsdw]

Good spot; thank you!

[pmikolajczyk41]

fixed, thanks!