improvement(state/core_access): remove defaultSignerAccount and defaultSignerAddress in favor and use app.ClientTx instead

[vgonkivs]

We can get rid of these two fields inside core_access and ru-use clientTx. Since the node's version of the app contains a small bug in handling DefaultAccountAddress(), it should be done after celestiaorg/celestia-app#3597 is included in app release.

Lets also use only user.WithDefaultAccount(keyName) in SetupTxClient

[MukulKolpe]

Hey @vgonkivs, can I work on this issue?

[vgonkivs]

Hello, @MukulKolpe. These changes haven't been released yet. Also this issue is blocked by #3349

[vgonkivs]

Hello @MukulKolpe. Do you still want to work on this issue?

[MukulKolpe]

Yes, I am still interested in working on this issue.

[vgonkivs]

Awesome. Thank you so much. Do not hesitate to ask any questions.

[vgonkivs]

After adding a retry mechanism for creating a TxClient, this issue becomes not relevant anymore.