Update to upstream scale-bits, scale-decode and scale-encode

[haerdib]

Parity has agreed to make these crates no_std compatible. Once the PRs have been merged, we should change the scale-... branches back to upstream (currently pointing to a fork), resp. to the newly published version on crates.io

• scale bits has been released in no_std: https://crates.io/crates/scale-bits: v0.4.0
• scale-decode: Add no-std compatibility paritytech/scale-decode#26 (current crates.io version: 0.7.0)
• scale-encode: Add no-std compatibility paritytech/scale-encode#11, merged, but not yet released on crates.io (current version: 0.3.0)

[jsdw]

Just to say, scale-decode 0.8 and scale-encode 0.4 are now released with no_std compat; thanks for your contributions! :)