test: tastora framework cleanup

[gupadhyaya]

Improvements:

• the framework should always have a single BN that is the minimum viable DA network (can keep it as pointer on the framework struct) and acts as the main entrypoint to the network for DA blocks/headers
• SetupNetwork should always set up the main BN as no DA tests can function without one
• can also have a separate field for additional BNs that are needed for other tests with more complex topology requirements
• a separate field for all LNs (as 1 or several may be required for tests)
• currently the api for creating / getting BNs and LNs is a bit all over the place; please separate into new (should include implicit start) — we may need to rethink this with certain topology / more complicated tests but let’s implicit start inside of New for now
• all funding endpoints should be private to framework and should not need to be touched outside of setting up blob submission (to fill up network)
• let’s just hide / unify most of this functionality until we define a concrete set of test cases to test blob submission from DA nodes
• generally, remove all unused methods on framework