Precompiled queries: only process queries for the specific context type

[AndriySvyryd]

When encountering a query for a different context this exception is currently thrown:

QueryPrecompilationError { SyntaxNode = context.Blogs.Count(), Exception = System.InvalidOperationException: Encountered unknown identifier name 'context', which doesn't correspond to a lambda parameter or captured variable
   at Microsoft.EntityFrameworkCore.Query.Internal.CSharpToLinqTranslator.VisitIdentifierName(IdentifierNameSyntax identifierName)
   at Microsoft.CodeAnalysis.CSharp.Syntax.IdentifierNameSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor`1.Visit(SyntaxNode node)
   at Microsoft.EntityFrameworkCore.Query.Internal.CSharpToLinqTranslator.Visit(SyntaxNode node)
   at Microsoft.EntityFrameworkCore.Query.Internal.CSharpToLinqTranslator.VisitMemberAccessExpression(MemberAccessExpressionSyntax memberAccess)
   at Microsoft.CodeAnalysis.CSharp.Syntax.MemberAccessExpressionSyntax.Accept[TResult](CSharpSyntaxVisitor`1 visitor)
   at Microsoft.CodeAnalysis.CSharp.CSharpSyntaxVisitor`1.Visit(SyntaxNode node)
   at Microsoft.EntityFrameworkCore.Query.Internal.CSharpToLinqTranslator.Visit(SyntaxNode node)