* master: (88 commits)
  upstream: Null-deref on TCP health checker if setsockopt fails  (envoyproxy#6793)
  ci: switch macOS CI to azure pipelines (envoyproxy#6889)
  os syscalls lib: break apart syscalls used for hot restart (envoyproxy#6880)
  Kafka codec: precompute request size before serialization, so we do n… (envoyproxy#6862)
  upstream: move static and strict_dns clusters to dedicated files (envoyproxy#6886)
  Rollforward of api: Add total_issued_requests to Upstream Locality and Endpoint Stats. (envoyproxy#6692) (envoyproxy#6784)
  fix explicit constructor in copy-initialization (envoyproxy#6884)
  stats: use tag iterator rather than constructing the tag-array and searching that. (envoyproxy#6853)
  common: use unscoped build target in generate_version_linkstamp (envoyproxy#6877)
  Addendum to envoyproxy#6778 (envoyproxy#6882)
  ci: add minimum Linux build for Azure Pipelines (envoyproxy#6881)
  grpc: utilities for inter-converting grpc::ByteBuffer and Buffer::Instance. (envoyproxy#6732)
  upstream: allow excluding hosts from lb calculations until initial health check (envoyproxy#6794)
  stats: prevent unused counters from leaking across hot restart (envoyproxy#6850)
  network filters: add `injectDataToFilterChain(data, end_stream)` method to network filter callbacks (envoyproxy#6750)
  delete things that snuck back in (envoyproxy#6873)
  config: scoped rds (2b): support delta APIs in ConfigProvider framework (envoyproxy#6781)
  string == string! (envoyproxy#6868)
  config: add mssing imports to delta_subscription_state (envoyproxy#6869)
  protobuf: add missing default case to enum (envoyproxy#6870)
  ...

Signed-off-by: Michael Puncel <mpuncel@squareup.com>