[release/9.0] Correct VisitUnary operand evaluation in funcletizer (#35172)

[roji]

Fixes #35152
Port of #35172

Description
In 9.0, EF's funcletizer was rewritten for performance and NativeAOT support; this is the very first component that processes the incoming expression tree, extracting parameters and performing other important tasks. In the new implementation, processing of unary expression nodes was faulty, not setting the expression visitor's state properly.

Customer impact
For various query types involving unary expression nodes (e.g. Convert), the query fails to translate. For example, in the following query type, the cast to object is a mishandled unary node:

var v = 1;
var q = await context.Set<Blog>().OrderBy(x => (object)v).ToListAsync();

As this querying scenario seems somewhat common, and the fix is very low-risk (add missing Convert node), it seems like this is a good candidate for servicing.

How found
Customer reported on 9.0.0

Regression
Yes, from 8.0.

Testing
Test added.

Risk
Low, quirk added.