Feat(CLI): add output type to all relevant commands

[willemneal]

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          Would be great for consistency (and usefulness) to add `--output xdr-base64` to other commands with a `--output` flag, like `contract read`, `events`, (and eventually `invoke`?)

Originally posted by @paulbellamy in https://github.com/stellar/soroban-tools/pull/829#pullrequestreview-1561037749