deprecate export of utils.escape/unescape #1758
Description
People should be using MarkupSafe instead. These utilities are here just to escape output in the debugger (and utils.HTMLBuilder, which should probably also be deprecated), where performance isn't really important. To keep them for internal use, rename them to _internal._escape and make utils.escape import that and show a deprecation warning pointing to MarkupSafe. Make sure to update use in the docs too.