[K8s][Tests] Add API to reset the network state for E2E tests

[okdas]

Objective

We need a way to reset the network to a particular genesis app state to run specific tests (e.g. there should be a staked actor to unstake it).

Origin Document

https://www.notion.so/K8sNet-0bc00f33aa4549e7acf4e70be78c6cfc?pvs=4

Goals

• Expose an API to reset the network.
• Ideally, this API should work on both DevNet and LocalNet.
• We need e2e tests isolated. Only after that work is done, we can have an isolated e2e tests.

Deliverables

• A testutil package that restarts the validator with a desired state.

Non-goals / Non-deliverables

• Switching tests to actually use this package. That work comes later.

General deliverables

• Comments: Add/update TODOs and comments alongside the source code so it is easier to follow.
• Testing: Add new tests (unit and/or E2E) to the test suite.
• Makefile: Add new targets to the Makefile to make the new functionality easier to use.
• Documentation: Update architectural or development READMEs; use mermaid diagrams where appropriate.

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Creator: @okdas