Add nameless decode to BaseContract

[halo3mic]

Motivation

BaseContract provides various methods for decoding input data: decode, decode_raw, decode_with_selector and decode_with_selector_raw.
These methods take a method name as an argument, which could be omitted as it is already provided through input-data.

Solution

Add new methods that decode input-data without requiring method-name as a parameter - decode_input_raw and decode_input.

Existing decode methods (decode, decode_raw, decode_with_selector and decode_with_selector_raw) lose functionality with the introduction of nameless decode methods. They could be removed unless I missed a viable utility or should be left in for backward compatibility.

PR Checklist

• Added nameless decode methods to BaseContract
• Add test
• Remove existing decode methods?

[prestwich]

needs formatting with cargo +nightly fmt

[prestwich]

concept ACK. See comment re rustfmt

[prestwich]

examples failure is unrelated