Add support for vouch remote proposers config

[corverroos]

Problem to be solved

Adds support for vouch remote proposer config to enable/disable buiderAPI.

Proposed solution

Add an endpoint similar to tekuProposerConfig that servers the vouch config.

[boulder225]

Removing it from the current sprint since Charon cannot introduce support for remote proposers config until Vouch adds support for that feature. @xenowits @thomasheremans FYI