Add contract alias add.

[fnando]

What

$ cargo run contract alias add increment --id CDUQDWIBBXWYHEEROXASCIBNZOZ45WJ3EOMAGMG4VTY36O2SGQTWCM23 --network testnet --global --overwrite
   Compiling soroban-cli v21.4.1 (/Users/fnando/Projects/stellar/stellar-cli/cmd/soroban-cli)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 4.09s
     Running `target/debug/soroban contract alias add increment --id CDUQDWIBBXWYHEEROXASCIBNZOZ45WJ3EOMAGMG4VTY36O2SGQTWCM23 --network testnet --global --overwrite`
ℹ️ Contract alias 'increment' will reference CDUQDWIBBXWYHEEROXASCIBNZOZ45WJ3EOMAGMG4VTY36O2SGQTWCM23 on network 'Test SDF Network ; September 2015'
✅ Contract alias 'increment' has been added

$ cargo run contract alias add increment --id CALLOOCCCJRZ6AZAJSKNCTDZ766N4ANVRKRJPHC65KDV7RJCS37PS4XY --network testnet --global
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.22s
     Running `target/debug/soroban contract alias add increment --id CALLOOCCCJRZ6AZAJSKNCTDZ766N4ANVRKRJPHC65KDV7RJCS37PS4XY --network testnet --global`
error: alias 'increment' is already referencing contract 'CDUQDWIBBXWYHEEROXASCIBNZOZ45WJ3EOMAGMG4VTY36O2SGQTWCM23' on network 'Test SDF Network ; September 2015'

$ cargo run contract alias add increment --id CALLOOCCCJRZ6AZAJSKNCTDZ766N4ANVRKRJPHC65KDV7RJCS37PS4XY --network testnet --global --overwrite
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.18s
     Running `target/debug/soroban contract alias add increment --id CALLOOCCCJRZ6AZAJSKNCTDZ766N4ANVRKRJPHC65KDV7RJCS37PS4XY --network testnet --global --overwrite`
ℹ️ Contract alias 'increment' will reference CALLOOCCCJRZ6AZAJSKNCTDZ766N4ANVRKRJPHC65KDV7RJCS37PS4XY on network 'Test SDF Network ; September 2015'
✅ Contract alias 'increment' has been added

$ cargo run contract alias add increment --id invalid --network testnet --global --overwrite
   Compiling soroban-cli v21.4.1 (/Users/fnando/Projects/stellar/stellar-cli/cmd/soroban-cli)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 3.17s
     Running `target/debug/soroban contract alias add increment --id invalid --network testnet --global --overwrite`
error: invalid value 'invalid' for '--id <CONTRACT_ID>': the strkey is invalid

For more information, try '--help'.

$ cat ~/.config/soroban/contract-ids/increment.json
{"ids":{"Test SDF Network ; September 2015":"CALLOOCCCJRZ6AZAJSKNCTDZ766N4ANVRKRJPHC65KDV7RJCS37PS4XY"}}

Why

#1420

Known limitations

N/A

[leighmcculloch]

"has been" is unnecessary.

Suggested change

	print.checkln(format!("Contract alias '{alias}' has been added"));
	print.checkln(format!("Contract alias '{alias}' added"));