Shell/RPC: add source argument for monitor_operations RPC

What

monitor_operation RPC can be filtered by sources.

Why

UX enhancement

How

Manually testing the MR

In sandbox mode once activated alpha,

curl -s localhost:18731/chains/main/mempool/monitor_operations\?sources\=<hash>

curl -s localhost:18731/chains/main/mempool/monitor_operations\?sources\=<hash1>\&sources\=<hash2>

replacing <hash> with tz1 you want to monitor. The RPC first send the list (potentially empty) of monitored tz1 operations inside the mempool, and will then send an operation each time it handles a new operation from monitored tz1. One can inject operations from monitored tz1 (operations are streamed) and from other tz1 (operations are not streamed).

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR