NTX Builder: Prune strategy for notes

[SantiagoPittella]

In #1892 I propose to store the committed notes in the NTX builder store, this causes some duplication with the store component.

We could try a couple different approaches to address this:

• We could add a timestamp to the entries, and considering that this endpoint is meant for debugging we can prune every period of time the old entries.
• Another option could be to check in the RPC component if we have that note committed in the store component before sending the request to the NTX builder.

[bobbinth]

I think the first option (pruning committed notes after some time) is probably the way to go (since indeed, the primary use case of this endpoint is debugging).