Add metrics to the job queue

This adds:

 - a histogram of the time it takes to process a job for each queue,
   with the status of the job (success, failure, etc.)
 - a histogram which records the time it takes to do a "tick", fetch jobs
 - a counter of the number of jobs currently in-flight for each queue
 - a counter which tracks the reasons why the worker got worken up

crates/tasks/Cargo.toml

@@ -29,6 +29,7 @@ tower.workspace = true
 tracing.workspace = true
 tracing-opentelemetry.workspace = true
 opentelemetry.workspace = true
+opentelemetry-semantic-conventions.workspace = true
 ulid.workspace = true
 url.workspace = true
 serde.workspace = true