Add releasenotes for recently added fixes

Conflicts:
  releasenotes/notes/sqlalchemy-20-abaa3d2895131ab4.yaml

Dropped one releasenote that doesn't apply to stable branches and
amended the title of the commit message for the backport.

Signed-off-by: Dr. Jens Harbott <harbott@osism.tech>
Change-Id: I856af3f0143e75253d001b50e70a418c1cac89f6
(cherry picked from commit abfd71ce42)

releasenotes/notes/rpc-workers-4941f3b9136418df.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    The BGP service plugin RPC queue has been added to RPC workers, like
+    it is done in other Neutron service plugins (l3-plugin, metering, etc.).
+    This fixes RPC requests and AMQP heartbeats not getting processed in
+    time, causing AMQP connection dropping, and other unpredictable unwanted
+    behavior.
+    See bug `1974057 <https://bugs.launchpad.net/neutron/+bug/1974057>`_.

releasenotes/notes/static-scheduler-2288b8173f9357a6.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Multiple issues in the implementation of the StaticScheduler have been
+    fixed that may have caused peers to be erroneously descheduled.
+    See bug `1980235 <https://bugs.launchpad.net/neutron/+bug/1980235>`_.