Updates for bdk-ffi v0.26

[BitcoinZavior]

Updates to add API from bdk ffi v0.26

Also Fixes #40: All the main errors mentioned in the bdk docs are custom exceptions in a readable format.

Updated Rust BDK FFI ( Bdk to latest version 0.26.0 ) and Flutter dependencies.

APIs changed

• The descriptor and changeDescriptor arguments on the wallet constructor now take a Descriptor instead of a String.

APIs added

• Added RpcConfig, BlockchainConfig.rpc
• Added Descriptor type with the following named constructors:
• Default create constructor, that requires a descriptor in String format and a Network
• newBip44 constructor returns a Descriptor with structure pkh(key/44'/{0,1}'/0'/{0,1}/*)
• newBip44Public constructor returns a Descriptor with structure pkh(key/{0,1}/*)
• newBip49 constructor returns a Descriptor with structure sh(wpkh(key/49'/{0,1}'/0'/{0,1}/*))
• newBip49Public constructor returns a Descriptor with structure sh(wpkh(key/{0,1}/*))
• newBip84 constructor returns a Descriptor with structure wpkh(key/84'/{0,1}'/0'/{0,1}/*)
• newBip84Public constructor returns a Descriptor with structure wpkh(key/{0,1}/*)
• asString returns the public version of the output descriptor in String format
• asPrivateString returns the private version of the output descriptor if available, otherwise, return the public version

Fixed

• Dependencies Upgraded (Flutter Rust bridge)