feat!: have tx gov submit-proposal accept either new or legacy syntax

[JimLarson]

Have submit-legacy-proposal be an alias for submit-proposal. Invocations of the legacy syntax should either upgrade to the new syntax, or explicitly use submit-legacy-proposal. When all legacy usages have so migrated, this change can be dropped. See Agoric/agoric-sdk#8871.

Description

Refs: cosmos#8871

Alter the tx gov submit-proposal command so that it works either with the new or legacy syntax, and also alias it as submit-legacy-proposal. Users of the legacy command will continue to work as-is, but over time they should either explicitly use submit-legacy-proposal, or upgrade to the new syntax. When all call sites have done one or the other of these choices, we can drop our modification to this command.

The slight limitation of this approach is that you cannot name the new-syntax JSON file the same as one of the legacy subcommands.

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[JimLarson]

No new tests since this is meant to be backward-compatible.

[dckc]

It would take me a while to study this enough to give an "I understand this well enough to help maintain it" review.

If there's some urgency and an "I don't see any problems" approval is useful, LMK.

[JimLarson]

The golangci-lint failure is expected.

[michaelfig]

LGTM! Well done.