ESQL: rename `INLINESTATS` to `INLINE STATS`

[bpintea]

Description

The space [is] to denote the same command [as STATS] just different semantic of summarising vs. not. [B]ut all rest of functionality is the same.
This is still STATS.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[getkub]

should this be better called as STATS itself with a separate mode?

For instance

|  STATS mode=inline  count(*) as count, max(salary) as max_salary by employee

so if you don't put mode=inline, then it means it will be normal stats

[bpintea]

should this be better called as STATS itself with a separate mode?

It is a different command, we'll want to make that clear, it has different semantics.