integration/internal: JobComplete: require shallower interface

client: separate Dialer() implementation from public API

client: move resetting mediaType for hijack to where applicable

The mediaType is only used in a single location; reset it in
that location.

client: make setupHijackConn a regular function

pass the dialer as argument

client: define separate interface for HijackDialer

client: define interface for all Swarm-specific methods

Introduce a SwarmManagementAPIClient interface that captures
all swarm-specific methods on the API client.

client: deprecate CommonAPIClient interface

The CommonAPIClient was used to define all the stable interfaces,
and combined with the experimental ones through APIClient. In theory,
this would allow someone to make sure they only depended on non-experimental
methods or to implement an alternative client that only implements the
stable methods.

While there are users currently using this interface, all those uses
depend on the actual client implementation, not a custom one, so they
should be able to switch to use APIClient instead. In the meantime,
start with deprecating, but keeping the interface the same for now,
scheduling it to become an alias, and removed in a future release.

- Human readable description for the release notes

- Go SDK: client: deprecate CommonAPIClient interface in favor of the APIClient interface. The CommonAPIClient will be changed to an alias for APIClient in the next release, and removed in the release after.
- Go SDK: client: add HijackDialer interface
- Go SDK: client: add SwarmManagementAPIClient interface to describe all API client methods related to swarm-specific objects.

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