hg-core: implement timestamp line parsing

doc: document that labels must have a dot in them to have an effect I noticed that the `hg topics` template has a bare `topic` label with no dot, and that makes it useless, as such a label will never receive any effect by the colour extension. This dot has been required for a long time, at least since 2011, but we never formally documented it!

tests: tweak chg test to make it fail less often the test apparently sometimes prints the word "start" as a part of profile, so let's no longer match "start": CHGHG=/*/install/bin/hg (glob) + \x1b[90m | 50.0% 0.01s profiling.py: __enter__ line 196: self.start()\x1b[0m (esc) + \x1b[90m | 50.0% 0.01s profiling.py: start line 261: self._profiler.__enter__()\x1b[0m (esc) + \x1b[90m | 50.0% 0.01s profiling.py: statprofile line 125: statprof.start(mechanism=b'...\x1b[0m (esc) + \x1b[90m | 50.0% 0.01s statprof.py: start line 356: state.thread.start()\x1b[0m (esc) + \x1b[90m | 50.0% 0.01s threading.py: start line 852: self._started.wait()\x1b[0m (esc)

cext: fix potential memory leaks of list items appended with PyList_Append Also reduce the duplication in the tricky code that uses PyList_Append by extracting it into a function `pylist_append_owned`.

crecord: enable search hotkeys (issue6834) The keys I chose here should be similar to less/vim keybindings, which should fit the overall keybinding theme of crecord.

crecord: add handle(next|prev)search functions These are now just simple wrappers around `searchdirection`

crecord: add a searchdirection function If a regex has already been previously set, this function handles the UI elements of searching again forward or backward.

crecord: add a handlesearch function This function sets up some of the UI, such as getting the search string from the user and displaying results or their absence.

crecord: add a showsearch function This function takes a regex and searches either forward or backward, moving the current item to the found item, if any, and unfolding the relevant context.

crecord: add a default regex to curseschunkselector Whether there is a regex to search or not will affect if we can find the next or the previous search hit.