feat: Add Textual SignModeHandler

[amaury1093]

Description

Closes: #13700

Tests will be added once the client-side infra is done, tracked by #13747

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[julienrbrt]

Do you think there is something to be updated here https://docs.cosmos.network/main/run-node/txs and https://docs.cosmos.network/main/modules/auth/tx given that it's now wired?

[amaury1093]

Do you think there is something to be updated here https://docs.cosmos.network/main/run-node/txs and https://docs.cosmos.network/main/modules/auth/tx given that it's now wired?

Textual is wired but not enabled by default, and I would keep it like this. I would even avoid any docs on how to enable it right now, as we're still testing it.

My initial plan was to finish Textual QA first, then enable it. I have an item in #11970 to add docs during the QA phase.