Remove legacy governance v1beta1 proposal handlers

[crodriguezvega]

Part of #1282.

Pre-requisites:

• Add message and rpc handler to recover clients using v1 governance proposals #3672
• Add message and rpc handler to upgrade clients using v1 governance proposals #3673

Overview of changes:

• Mark ClientUpdateProposal and UpgradeProposal messages as deprecated with adding option deprecated = true;.
• Remove proposal handlers in app.go.
• Remove call to NewClientProposalHandler in app.go.
• Remove ClientUpdateProposal implementation registration and UpgradeProposal implementation registration.
• Remove NewUpgradeClientCmd and NewCmdSubmitUpdateClientProposal.
• Remove files modules/core/02-client/keeper/proposal.go and modules/core/02-client/client/proposal-handler.go.
• Remove e2e test TestClientUpdateProposal_Succeeds.
• Update v8 migration docs, if needed.

[colin-axner]

We should migrate the proposals to messages first right? Maybe we can add those issues as pre reqs?

[crodriguezvega]

@womensrights verified that relayers are not using the CLI commands so we can remove them.

[colin-axner]

What's the benefit of marking protos as deprecated as opposed to removing entirely? I don't think we have an rpc for submitting the legacy proposal?

[colin-axner]

removed by #4581 and #4602, will be merged to main by #4620, migration docs will be handled by #4544