Support the case-sensitive table name and column name

[goldmedal]

Description

The model name and column name are currently case insensitive. The following model isn't valid now.

ModelBuilder::new("Customer")
    .table_reference("datafusion.public.customers")
    .column(ColumnBuilder::new("city", "varchar").build())
    .column(ColumnBuilder::new("id", "varchar").build())
    .column(ColumnBuilder::new("state", "varchar").build())
    .primary_key("id")
    .build(),

We don't support the name with the uppercase text.