Today we report thread pool info using a common object. This means that
we use a shared set of terminology that is not consistent with the
terminology used to the configure thread pools. This holds in particular
for the minimum and maximum number of threads in the thread pool where
we use the following terminology:
 thread pool info | fixed | scaling
  min                core    size
  max                max     size

A previous change addressed this for the nodes info API. This commit
changes the display of thread pool info in the cat thread pool API too
to be dependent on the type of the thread pool so that we can align the
terminology in the output of thread pool info with the terminology used
to configure a thread pool.

* master: (80 commits)
  Remove HTTP max content length leniency (elastic#29337)
  Begin moving XContent to a separate lib/artifact (elastic#29300)
  Java versions for ci (elastic#29320)
  Minor cleanup in the InternalEngine (elastic#29241)
  Clarify expectations of false positives/negatives (elastic#27964)
  Update docs on vertex ordering (elastic#27963)
  Revert "REST high-level client: add support for Indices Update Settings API (elastic#28892)" (elastic#29323)
  [test] remove Streamable serde assertions (elastic#29307)
  Improve query string docs (elastic#28882)
  fix query string example for boolean query (elastic#28881)
  Resolve unchecked cast warnings introduced with elastic#28892
  REST high-level client: add support for Indices Update Settings API (elastic#28892)
  Search: Validate script query is run with a single script (elastic#29304)
  [DOCS] Added info on WGS-84. Closes issue elastic#3590 (elastic#29305)
  Increase timeout on Netty client latch for tests
  Build: Use branch specific refspec sysprop for bwc builds (elastic#29299)
  TEST: trim unsafe commits before opening engine
  Move trimming unsafe commits from engine ctor to store (elastic#29260)
  Fix incorrect geohash for lat 90, lon 180 (elastic#29256)
  Do not load global state when deleting a snapshot (elastic#29278)
  ...

* master:
  Reindex: Fix error in delete-by-query rest spec (elastic#29318)
  Improve similarity integration. (elastic#29187)
  Fix some query extraction bugs. (elastic#29283)
  [Docs] Correct experimental note formatting
  Move Nullable into core (elastic#29341)
  [Docs] Update getting-started.asciidoc (elastic#29294)
  Elasticsearch 6.3.0 is now on Lucene 7.3.
  [DOCS] Refer back to index API for full-document updates in _update API section (elastic#28677)
  Fix missing comma in ingest-node.asciidoc (elastic#29343)
  Improve exception handling on TransportMasterNodeAction (elastic#29314)
  Don't break allocation if resize source index is missing (elastic#29311)
  Use fixture to test repository-s3 plugin (elastic#29296)
  Fix NDCG for empty search results (elastic#29267)
  Pass through script params in scripted metric agg (elastic#29154)
  Fix Eclipse build.
  Upgrade to lucene-7.3.0-snapshot-98a6b3d. (elastic#29298)
  Painless: Remove extraneous INLINE constant. (elastic#29340)