supergraph coprocessor followup, with docs update and changelog update

[o0Ignition0o]

This is a followup to #3408 that:

• removes the path variable,
• makes sure we only send the sdl and method if they're enabled in the configuration
• updates the documentation to reflect that.

This doesn't need a changelog entry because it is covered by the previous PR.

[router-perf]

CI performance tests

• xxlarge-request - Stress test with 100 MB request payload
• step - Basic stress test that steps up the number of users over time
• events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• events - Stress test for events with a lot of users and deduplication ENABLED
• large-request - Stress test with a 1 MB request payload
• const - Basic stress test that runs with a constant number of users
• no-graphos - Basic stress test, no GraphOS.
• reload - Reload test over a long period of time at a constant rate of users
• step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• xlarge-request - Stress test with 10 MB request payload
• events_big_cap_high_rate - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity

[o0Ignition0o]

Closed in favor of reverting the supergraph coprocessor pr and reopening it cleanly for 1.28