Add a CI workflow for getblocktemplate-rpcs feature

[oxarbitrage]

After #5357 gets merged we want to add a workflow into the CI so we can:

• Build the code inside that feature
• Run the test code behind this feature

To do this, we'll need to:

• Add a getblocktemplate-rpcs feature to zebrad that activates the zebra-rpc feature

[teor2345]

@mpguerra this ticket was split out of #5305, can we schedule it in this sprint?

[mpguerra]

@mpguerra this ticket was split out of #5305, can we schedule it in this sprint?

Sure, it will need an estimate though :)

[mpguerra]

Hey team! Please add your planning poker estimate with Zenhub @arya2 @conradoplg @oxarbitrage @teor2345 @upbqdn