Add query root rewrite support

tests/EntityFrameworkCore.Projectables.FunctionalTests/QueryRootTests.UseMemberPropertyQueryRootExpression.verified.txt

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+SELECT [e].[Id], [e].[Id] * 5
+FROM [Entity] AS [e]

tests/EntityFrameworkCore.Projectables.FunctionalTests/QueryRootTests.cs

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+using System.ComponentModel.DataAnnotations.Schema;
+using System.Threading.Tasks;
+using EntityFrameworkCore.Projectables.FunctionalTests.Helpers;
+using Microsoft.EntityFrameworkCore;
+using VerifyXunit;
+using Xunit;
+
+namespace EntityFrameworkCore.Projectables.FunctionalTests
+{
+    [UsesVerify]
+    public class QueryRootTests
+    {
+        public record Entity
+        {
+            public int Id { get; set; }
+
+            [Projectable(UseMemberBody = nameof(Computed2))]
+            public int Computed1 => Id;
+
+            private int Computed2 => Id * 2;
+
+            [Projectable(UseMemberBody = nameof(_ComputedWithBaking))]
+            [NotMapped]
+            public int ComputedWithBacking { get; set; }
+
+            private int _ComputedWithBaking => Id * 5;
+        }
+
+        [Fact]
+        public Task UseMemberPropertyQueryRootExpression()
+        {
+            using var dbContext = new SampleDbContext<Entity>();
+
+            var query = dbContext.Set<Entity>();
+
+            return Verifier.Verify(query.ToQueryString());
+        }
+    }
+}