Move libs to libs/celestia-app

[Manav-Aggarwal]

We have code that was imported into rollkit from celestia-app in 888 as part of unlocking 889. We plan to later extract this common code into a separate repo that both celestia-app and rollkit can use.

For now, we'd like to adopt a standard of libs//... so that when we are reviewing code it is clearer what code is a copy-paste in from other libraries and needs to extracted out as part of good code-hygiene and keep the code more maintainable.

We should start adopting this standard by moving code under libs to libs/celestia-app.