Add support for alias on `stellar contract fetch`. #446

Job	Run time
build (stellar-cli, stellar, ubuntu-20.04, x86_64-unknown-linux-gnu)	13m 36s
build (stellar-cli, stellar, ubuntu-20.04, aarch64-unknown-linux-gnu)	15m 12s
build (stellar-cli, stellar, macos-14, x86_64-apple-darwin)	8m 51s
build (stellar-cli, stellar, macos-12, aarch64-apple-darwin)	14m 41s
build (stellar-cli, stellar, windows-latest, x86_64-pc-windows-msvc, .exe)	22m 7s
build (soroban-cli, soroban, ubuntu-20.04, x86_64-unknown-linux-gnu)	13m 57s
build (soroban-cli, soroban, ubuntu-20.04, aarch64-unknown-linux-gnu)	15m 48s
build (soroban-cli, soroban, macos-14, x86_64-apple-darwin)	10m 11s
build (soroban-cli, soroban, macos-12, aarch64-apple-darwin)	13m 4s
build (soroban-cli, soroban, windows-latest, x86_64-pc-windows-msvc, .exe)	20m 50s
	2h 28m 17s

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