Account recovery improvements

[AArnott]

This pull request includes several changes to the Nerdbank.Zcash project, mainly focusing on transaction handling and data structures. The changes include the addition of a Pool enum and its integration into the TransactionNote struct, modifications to the Transaction class in Transaction.cs, and alterations to SQL statements in sql_statements.rs.

Changes to data structures:

• src/nerdbank-zcash-rust/src/interop.rs: Added a Pool enum and integrated it into the TransactionNote struct. [1] [2]
• src/nerdbank-zcash-rust/src/ffi.udl: Added a Pool enum and integrated it into the TransactionNote dictionary. [1] [2]
• src/Nerdbank.Zcash/RustBindings/LightWallet.cs: Added a Pool enum and integrated it into the TransactionNote record. [1] [2] [3]
• src/Nerdbank.Zcash/Transaction.cs: Added a DebuggerDisplay attribute to the Transaction class and a DebuggerDisplay property. [1] [2]

Changes to transaction handling:

• src/Nerdbank.Zcash/LightWalletClient.cs: Modified the CreateLineItem method to handle excess receivers and use standard encodings for each pool.
• src/nerdbank-zcash-rust/src/sync.rs: Made changes to the get_transactions function to accommodate the new Pool enum and handle transactions accordingly. [1] [2] [3] [4] [5]

Changes to SQL statements:

• src/nerdbank-zcash-rust/src/sql_statements.rs: Modified the GET_TRANSACTIONS_SQL constant to accommodate changes in transaction handling. [1] [2]