release-23.1: rpc: use the loopback conn also for GRPCDialOptions

[blathers-crl]

Backport 1/1 commits from #103764 on behalf of @knz.

/cc @cockroachdb/release

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Fixes #103762.
Fixes #99261.
Fixes #103692.

For context, rpc.GRPCDialOptions is used in two cases:

• when connecting to other nodes as specified by the --join flag.
• in the grpc-gateway code, to route incoming HTTP requests to the RPC subsystem.

The first one nearly always targets remotes nodes. The second one always targets the local node (it's a loopback connection).

Prior to this patch, the 2 callers to rpc.GRPCDialOptions would be served the regular "remote network conn" dial options unconditionally, including the backoff, only-once-dialer and other parameters suitable to connect to other nodes remotely.

While this choice is suitable for the --join logic, it's not suitable for the grpc-gateway loopback conn. In that case, we want to avoid all the network intelligence and especially avoid the only-once-dialer and circuit breaker.

This patch ensures that grpc-gateway receives the loopback parameters properly.

Release note (bug fix): A bug was fixed whereby under high CPU load,
HTTP requests to certain API endpoints (e.g. the health endpoint)
could start failing and then never succeed again until the node was
restarted. This bug had been introduced in v23.1.

---

Release justification: fixes major regression in 23.1

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is