make resolvers configurable

[zoedberg]

With this PR we allow RGB users to set a custom configuration for the resolvers. This feature could be useful especially for mobile clients, where the default timeout (30 seconds) could be too high.

Since electrum and esplora crates have different ways to instantiate a new client I've also made this https://github.com/BP-WG/bp-esplora-client/pull/5 to add a Config to esplora, making it more similar to the electrum client. For this reason this PR is in draft, once that will be merged I'll revert the patch and undraft this.

Note: this PR also fixes the build (which was broken due to a force push in bp-core).