[DOC] Clarify ThreadPools

[stefnestor]

request

Howdy! I have questions on this following doc: Thread Pools. My poor-man's reading indicates rows may be missing when comparing doc to code to my localhost api response. Can you help fill in remaining missing content / reason non-applicable?

data

thread_pool	doc	code	api	type	doc description
analyze	t	t	t	scaling	For analyze requests.
auto_complete	FALSE	t	t	fixed
ccr	FALSE	FALSE	t	fixed
fetch_shard_started	t	t	t	scaling	For listing shard states.
fetch_shard_store	t	t	t	scaling	For listing shard stores.
flush	t	t	t	scaling	For flush, synced flush, and translog fsync operations.
force_merge	t	t	t	fixed	For force merge operations.
generic	t	t	t	scaling	For generic operations (for example, background node discovery).
get	t	t	t	fixed	For get operations.
listener	t	FALSE	t	fixed	Mainly for java client executing of action when listener threaded is set to true.
management	t	t	t	scaling	For cluster management.
ml_datafeed	FALSE	FALSE	t	scaling
ml_job_comms	FALSE	FALSE	t	scaling
ml_utility	FALSE	FALSE	t	scaling
refresh	t	t	t	scaling	For refresh operations.
rollup_indexing	FALSE	FALSE	t	fixed
same	FALSE	t	FALSE	fixed
search_coordination	FALSE	t	FALSE	fixed
search_throttled	t	t	t	fixed_auto_queue_size	For count/search/suggest/get operations on search_throttled indices.
search	t	t	t	fixed_auto_queue_size	For count/search/suggest operations.
searchable_snapshots_cache_fetch_async	FALSE	FALSE	t	scaling
searchable_snapshots_cache_prewarming	FALSE	FALSE	t	scaling
security-crypto	FALSE	FALSE	t	fixed
security-token-key	FALSE	FALSE	t	fixed
snapshot_meta	t	t	t	scaling	For snapshot repository metadata read operations.
snapshot	t	t	t	scaling	For snapshot/restore operations.
system_critical_read	t	t	t	fixed	For critical read operations on system indices.
system_critical_write	t	t	t	fixed	For critical write operations on system indices.
system_read	t	t	t	fixed	For read operations on system indices.
system_write	t	t	t	fixed	For write operations on system indices.
transform_indexing	FALSE	FALSE	t	fixed
vector_tile_generation	FALSE	FALSE	t	fixed
warmer	t	t	t	scaling	For segment warm-up operations.
watcher	t	FALSE	t	fixed	For watch executions.
write	t	t	t	fixed	For single-document index/delete/update and bulk requests.

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[stefnestor]

Appending that on at least 2 test v8.1.0 deployments, thread pools appear to add [azure_event_loop,repository_azure], and subtract [listener,same,transform_indexing].