PYTHON-5668 - Merge backpressure branch into mainline (#2729)

Co-authored-by: Steven Silvester <steve.silvester@mongodb.com>
Co-authored-by: Shane Harvey <shnhrv@gmail.com>
Co-authored-by: Steven Silvester <steven.silvester@ieee.org>
Co-authored-by: Iris <58442094+sleepyStick@users.noreply.github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Kevin Albertson <kevin.albertson@mongodb.com>
Co-authored-by: Casey Clements <caseyclements@users.noreply.github.com>
Co-authored-by: Sergey Zelenov <mail@zelenov.su>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 9 people

.evergreen/resync-specs.sh

@@ -94,6 +94,9 @@ do
     change-streams|change_streams)
       cpjson change-streams/tests/ change_streams/
       ;;
+    client-backpressure|client_backpressure)
+      cpjson client-backpressure/tests client-backpressure
+      ;;
     client-side-encryption|csfle|fle)
       cpjson client-side-encryption/tests/ client-side-encryption/spec
       cpjson client-side-encryption/corpus/ client-side-encryption/corpus