fix(filter): resolve non-public members like v1.14.2

[pdevito3]

Summary

This PR restores D1 from the v1.14.2 review report. It is not a breaking change.

v1.14.2 resolved each filter segment with Expression.PropertyOrField. Main resolves only public members. As a result, main rejects filters on internal, protected, and private members that v1.14.2 accepted. Main also treats an indexer (Item) as a member and throws ArgumentException.

This PR makes PropertyResolver use the lookup order of Expression.PropertyOrField, ignoring case:

1. A public property
2. A public field
3. A non-public property
4. A non-public field

An indexer does not match. It is an unknown property again.

Results against v1.14.2

Input	v1.14.2	main	This PR
InternalScore > 30 (internal property)	x.InternalScore > 30	UnknownFilterPropertyException	same as v1.14.2
secretRank == 7 (private field)	x.secretRank == 7	UnknownFilterPropertyException	same as v1.14.2
ProtectedNote == "a"	filters	throws	same as v1.14.2
Author.InternalAlias == "Ann"	filters	throws	same as v1.14.2
secretRank > 100 with AllowUnknownProperties	x.secretRank > 100	True == True	same as v1.14.2
Item == "x" (indexer)	UnknownFilterPropertyException 'Item'	ArgumentException	same as v1.14.2
Item == "x" with AllowUnknownProperties	True == True	ArgumentException	same as v1.14.2

A differential probe ran 23 cases against v1.14.2 and this branch, on the expression, the in-memory rows, and the Postgres SQL. The only remaining difference is the in-list constant type for InternalScore ^^ [40, 50] (List against InListValues). PR #133 made that change on purpose, and it does not change the result or the SQL.

Tests

• Unit pins in QueryKit.UnitTests/PropertyResolverTests.cs: internal, protected, private, and nested internal members, a property list, a query name on an internal member, AllowUnknownProperties, the public-before-non-public order, and the indexer. 13 of these fail on main.
• Postgres pins in QueryKit.IntegrationTests/Tests/PropertyResolverTests.cs: a filter on an internal EF-mapped property, with and without AllowUnknownProperties. Both fail on main with UnknownFilterPropertyException.
• The test model gets an internal Nickname property on TestingPerson, mapped to a new nullable nickname column with a migration. QueryKit.WebApiTestProject makes its internals visible to the integration tests.
• dotnet test: unit 416 passed, integration 285 passed.

Overlap with other PRs

• D5: this PR also removes the indexer case of D5. The D5 PR (fix(filter): throw UnknownFilterPropertyException again for a failed query name filter #160) covers only the remaining cases.
• A separate breaking PR (fix(filter)!: resolve only public members #161), based on this branch, brings back the public-only lookup for a later major version.
• No README section documents member lookup, so the README does not change.