templatefilters: drop broken "jsonescape" from filters table (BC) It's been unused, undocumented and flawed in that it expects a unicode input, never works correctly if an input has non-ascii character. We should use "json" filter instead.

treemanifest: rewrite text() using iterentries() This simplifies a bit. Note that the function is only used when manually testing with _treeinmem=True.

treemanifest: implement iterentries() To make tests pass with _treeinmem manually set to True, we need to implement the recently added iterentries() on the treemanifest class too.