feat(server): start grpc server and register services in standalone mode

[p-offtermatt]

Description

Closes: #16277
Starts the gRPC server even when standalone mode is used.
Also registers services to expose over the gRPC server:
The CometBFT rpc endpoin t is assumed to be exposed at the rpc.laddr (which is where the cometBFT server started by the SDK would also expose the rpc server).

I tried this locally with CometMock and it fixes #16277: I tried grpcurl to call endpoints from cosmos.tx.v1beta1.Service, cosmos.base.node.v1beta1.Service/Status and cosmos.base.tendermint.v1beta1.Service

Is there any testing infrastructure set up to test out-of-process comet?
Then tests for this could hook in there.
If there are no tests for that anyways, I think this change isn't necessarily worth adding them for,
since it's relatively minimal.

This should be backported to v0.47 and v0.50. There is already a PR that aims to backport to v0.47 here:
#18109

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Author Checklist

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• included the correct type prefix in the PR title
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• followed the guidelines for building modules N/A
• included the necessary unit and integration tests N/A I think neither the standalone nor the in-process versions of start are tested in those tests. Please correct me if that's wrong
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
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[julienrbrt]

utACK!

[tac0turtle]

do you need the api server here as well?

[p-offtermatt]

Currently I don't. I'll let you decide whether you think this should still be started - I think the alternative is to have an issue for it and pick it back up if anyone asks for it at some point

[tac0turtle]

can we add a startAPI call, everything seems registered, for consistency and to avoid have another issue sitting for a while

[p-offtermatt]

Done, it's also starting the api server now