Prepare for non-Base58 addresses [Step 1]

[furszy]

This patch removes the need for the intermediary Base58 type CBitcoinAddress, by providing {Encode,Decode,IsValid} Destination functions that directly operate on the conversion between std::strings and CTxDestination.

As a side, it also fixes a number of indentation issues, and removes probably several unnecessary implicit CTxDestination<->CBitcoinAddress conversions.

It's not a small change but it will give us much more flexibility once it's fully done over every current and new address type.

The first commit is coming from upstream partially (11117), the rest is purely tackling our code (we have so so many more places using the CBitcoinAddress class).

And finally, have implemented a second abstraction (Destination wrapper) on top of the base58 address to {Encode,Decode,IsValid} Staking addresses as well.

Note:
This migration is not fully complete. It's first step, we still have places using the CBitcoinAddress object instead of the CTxDestination abstraction.

[furszy]

Rebased + rpc files CBitcoinAddress migration added.

[random-zebra]

Big PR. Good job 👍 We can (should) probably simplify and abstract some of the ugliness due to staking addresses with a better definition of them (either as variant or child class) in the future.

Anyway, looking good from visual inspection: concept and code ACK modulo some questions, comments and/or nits inlined.
Mostly around:

1. IsValidDestinationString formula for staking addresses with &&

2. The extra overridden version of IsValidDestinationString: we don't need params to be passed as an external argument to IsValid (at the moment). We should probably include that only when we remove the dependency from CChainParams

3. The usage of !boost::get<CNoDestination>(&address) instead of IsValidDestination(address). There are many instances, I haven't commented all of them.

4. a few double decoding operations due to the general path

   if (!IsValidDestinationString(address_string) {
       // return some error
   } 
   CTxDestination dest = DecodeDestination(address_string);
   ...
   

   which should be

   CTxDestination dest = DecodeDestination(address_string);
   if (!IsValidDestination(dest)) {
       // return some error
   }
   ...
   

[furszy]

Thanks for the feedback zebra, went commit by commit and solved most of them.

[furszy]

just force pushed it few times because found more boost::get to move to IsValidDestination.

It's good now.

[Fuzzbawls]

Nice one. Full sync check done now.

ACK ac99512

[random-zebra]

ACK ac99512 and merging...