297ab05ef converted CDS to XdsDependencyManager. This caused three
regressions:
* CdsLB2 as a RLS child would always fail with "Unable to find
non-dynamic root cluster" because is_dynamic=true was missing in
its service config
* XdsNameResolver only propagated resolution updates when the clusters
changed, so a CdsUpdate change would be ignored. This caused a hang
for RLS even with is_dynamic=true. For non-RLS the lack config update
broke the circuit breaking psm interop test. This would have been
more severe if ClusterResolverLb had been converted to
XdsDependenceManager, as it would have ignored EDS updates
* RLS did not propagate resolution updates, so CdsLB2 even with
is_dynamic=true the CdsUpdate for the new cluster would never arrive,
causing a hang
b/428120265
b/427912384