Investigate type usage of sp_runtime and sp_core

[haerdib]

As written here: #541 (comment)

subxt inserted this in paritytech/subxt@b316301#diff-57540144ef1381f66537718f59e717110353e5408cdf539b67f7a1ff9cdd0d10 to make sp_core and sp_runtime dependencies optional. See paritytech/subxt#760.
The Header trait has also been inserted for this purpose.
Removing these would certainly simplify our configurations and code. If our goal is to have an easy to use configuration, we should do it. But I like subxt idea of "Reducing the need to keep up to date with Substrate packlage versions". See PR paritytech/subxt#760

One should decide if it makes sense to completely remove sp_runtiem and sp_core dependency. But also the implications of it. See #391

[haerdib]

We decided to remove the duplicate types as much as possible but keep the deps instead.

[haerdib]

Pro for keeping it:

• No need for type updates in our own code base in case substrate updates the types
• less complicated for users: one type only
• More flexibility for users in types (full type information always available)

[haerdib]

Since we came to a conclusion, I'm closing this issue. The types will be removed in #391