chore(fields): Break up EVENT_FIELD_DEFINITIONS (#95841)

`EVENT_FIELD_DEFINITIONS` contain a lot of definitions for various
fields. It actually contains definitions for fields on different event
types. Because of this, the definitions are bleeding into other
datasets. For example, in the search bar in explore, if the user tries
to use the key `status`, it pulls in the definition of the status field
in errors mistakenly.

To remedy this, this PR starts by breaking `EVENT_FIELD_DEFINITIONS`
into smaller logical groups of field definitions. And I'll follow up by
properly assigning the right fields to the right event types.

Author: Zylphrex