[ES|QL] add more info to operator docs

[drewdaemon]

Description

We have two asks before we can pull the operator docs into Kibana's inline help.

1. We need some way to get the actual operator character (e.g. - for NEG)... maybe a new field in the operator definitions?
2. The following names should be expanded so they are more user-friendly.

• DIV -> DIVIDE
• MOD -> MODULO
• MUL -> MULTIPLY
• NEG -> NEGATE
• SUB - SUBTRACT

This will allow the titles of these sections to be much more helpful. For example NEG will become NEGATE (-).

[elasticsearchmachine]

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

[elasticsearchmachine]

Pinging @elastic/kibana-esql (ES|QL-ui)

[craigtaverner]

This was done as part of the work at #126279