Today we are strict when parsing build flavor and types off the
wire. This means that if a later version introduces a new build flavor
or type, an older version would not be able to parse what that new
version is sending. For a practical example of this, we recently added
the build type "docker", and this means that in a rolling upgrade
scenario older nodes would not be able to understand the build type that
the newer node is sending. This breaks clusters and is bad. We do not
normally think of adding a new enumeration value as being a
serialization breaking change, it is just not a lesson that we have
learned before. We should be lenient here though, so that we can add
future changes without running the risk of breaking ourselves
horribly. It is either that, or we have super-strict testing
infrastructure here yet still I fear the possibility of mistakes. This
commit changes the parsing of build flavor and build type so that we are
still strict at startup, yet we are lenient with values coming across
the wire. This will help avoid us breaking rolling upgrades, or clients
that are on an older version.

* master:
  add reason to DataFrameTransformState and add hlrc protocol tests (elastic#40736)
  Remove timezone validation on rollup range queries (elastic#40647)
  Fix testRunStateChangePolicyWithAsyncActionNextStep race condition (elastic#40707)
  Don't mark shard as refreshPending on stats fetching (elastic#40458)
  Name Snapshot Data Blobs by UUID (elastic#40652)
  SQL: [TEST] Mute TIME related failing tests
  [TEST] RecoveryWithConcurrentIndexing test (elastic#40733)

…leniency

* elastic/master:
  SQL: Fix deserialisation issue of TimeProcessor (elastic#40776)
  Improve GCS docs for using keystore (elastic#40605)
  Add Restore Operation to SnapshotResiliencyTests (elastic#40634)
  Small refactorings to analysis components (elastic#40745)
  SQL: Fix display size for DATE/DATETIME (elastic#40669)
  add HLRC protocol tests for transform state and stats (elastic#40766)
  Inline TransportReplAction#registerRequestHandlers (elastic#40762)
  remove experimental label from search_as_you_type documentation (elastic#40744)
  Remove some abstractions from `TransportReplicationAction` (elastic#40706)
  Upgrade to latest build scan plugin (elastic#40702)
  Use default memory lock setting in testing (elastic#40730)
  Add Bulk Delete Api to BlobStore (elastic#40322)
  Remove yaml skips older than 7.0 (elastic#40183)
  Docs: Move id in the java-api (elastic#40748)

* master: (63 commits)
  Suppress lease background sync failures if stopping (elastic#40902)
  [DOCS] Added settings page for ILM. (elastic#40880)
  [Docs] Remove extraneous text (elastic#40914)
  Move test classes to test root in Painless (elastic#40873)
  Fix date index name processor default date_formats (elastic#40915)
  Source additional files correctly in elasticsearch-cli (elastic#40890)
  Allow AVX-512 on JDK 11+ (elastic#40828)
  [Docs] Change example to show col headers (elastic#40822)
  Update apache httpclient to version 4.5.8 (elastic#40875)
  Update monitoring-kibana.json (elastic#40899)
  Introduce Delegating ActionListener Wrappers (elastic#40129)
  Deprecate old transport settings (elastic#40821)
  Add Kibana application privileges for monitoring and ml reserved roles (elastic#40651)
  Use Writeable for TransportReplAction derivatives (elastic#40894)
  Add test for HTTP and Transport TLS on basic license (elastic#40714)
  Remove unneded cluster config from test (elastic#40856)
  Make Fuzziness reject illegal values earlier (elastic#33511)
  Remove test-only customisation from TransReplAct (elastic#40863)
  Fix dense/sparse vector limit documentation (elastic#40852)
  Make -try xlint warning disabled by default. (elastic#40833)
  ...