[ES|QL] use getExpressionType in more places

[drewdaemon]

Describe the feature:

#195989 added a utility getExpressionType to determine the type of an expression. It has the potential to replace / be merged with similar routines in our validation/autocomplete code.

• extractTypeFromESNode — looks like a 1:1 substitution
• checkFunctionArgMatchesDefinition — pretty close to a 1:1 substitution: get the type from the AST using getExpressionType and then check it against the parameter definition.
• validateFunction — The function validation routine performs essentially the same traversal as getExpressionType while also generating error messages. Another difference is that validateFunction does checks on the way down, while getExpressionType computes the types on the way back up. Combining them could be great, but it is a stretch goal and I'm not absolutely certain it is the right thing to do.

[elasticmachine]

Pinging @elastic/kibana-esql (Team:ESQL)

[stratoula]

@drewdaemon can you give me a size estimation for this task?

[drewdaemon]

extractTypeFromESNode — looks like a 1:1 substitution
checkFunctionArgMatchesDefinition — pretty close to a 1:1 substitution: get the type from the AST using getExpressionType and then check it against the parameter definition.

^^ 2-3 days

validateFunction — The function validation routine performs essentially the same traversal as getExpressionType while also generating error messages. Another difference is that validateFunction does checks on the way down, while getExpressionType computes the types on the way back up. Combining them could be great, but it is a stretch goal and I'm not absolutely certain it is the right thing to do.

^^ not sure, more of an experiment