features: `relayers` Expose running arbitrary scripts or commands on nodes

[Anmol1696]

Overview

If one wants to create custom channels between the chains on the fly, then it is currently not possible.

Proposal

/command endpoint on the exposer to run custom scripts or commands directly on the relayers.

Alternatives

Currently we can still do this with kubectl exec. We can run this directly from a test case, although this will make it a bit messy.

[Anmol1696]

For the current use case, it might make more sense to have a helper function in all the clients to be able to perform exec commands.
Starting with Go client would make most sense.