Allow filtering operations by tool and invocation
This MR adds the ability to filter operations based on tool name and version, as well as the invocation_id and correlated_invocations_id set in the Execute request's metadata for a given operation.
This provides an easy way to get all the operations/actions for a given invocation of a tool that sends many Execute requests (such as Bazel or BuildStream).
A client could use this kind of filtering to compile a collection of all logs from a specific invocation of a tool, for example.
This resolves #360 (closed)