Add support for alias on `stellar contract fetch`. #442

Job	Run time
build (stellar-cli, stellar, ubuntu-20.04, x86_64-unknown-linux-gnu)	14m 3s
build (stellar-cli, stellar, ubuntu-20.04, aarch64-unknown-linux-gnu)	15m 21s
build (stellar-cli, stellar, macos-14, x86_64-apple-darwin)	9m 22s
build (stellar-cli, stellar, macos-12, aarch64-apple-darwin)	13m 10s
build (stellar-cli, stellar, windows-latest, x86_64-pc-windows-msvc, .exe)	21m 54s
build (soroban-cli, soroban, ubuntu-20.04, x86_64-unknown-linux-gnu)	13m 35s
build (soroban-cli, soroban, ubuntu-20.04, aarch64-unknown-linux-gnu)	15m 19s
build (soroban-cli, soroban, macos-14, x86_64-apple-darwin)	9m 8s
build (soroban-cli, soroban, macos-12, aarch64-apple-darwin)	18m 55s
build (soroban-cli, soroban, windows-latest, x86_64-pc-windows-msvc, .exe)	21m 6s
	2h 31m 53s

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