[release/9.0] Add missing Converts when simplifying in funcletizer (#35122)

[roji]

Fixes #35095
Port of #35122

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. For certain query scenarios, e.g. Coalesce operations which can be optimized away, a missing conversion node can cause an exception.

Customer impact

LINQ queries such as the following, where a nullable value type parameter is coalesced in the query, but can be optimized away (since the parameter is known to be non-null), fail to translate in 9.0:

int? test = 1;
var blog = context.Blogs.Where(b => b.Id == (test ?? 0)).ToList();

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.