annotate: migrate to modern pager API

ui: add a debug print right before we start the pager This makes it easier to figure out why a command is getting paginated.

ui: respect historic pager.attend-$COMMAND=no I'm on the fence about this behavior, but the user's intent was pretty specific and it's not expensive to support this case.

tests: clean up a bunch of pager testing that is about to be invalidated All this attend logic and potential bugs just no longer make sense to test.

ui: add ignore-single-command functionality This closes the last feature gap other than the attend list from the extension. For now, I'm leaving the attend list in the extension, because I'm unsure it has merit in a world where commands have been updated to take advantage of the modern API.

ui: introduce neverpager() call I'm about to add direct paging support to some commands, and as a result we need a way to communicate from the higher layers of dispatch that paging is explicitly disabled.

pager: move more behavior into core This moves the global flag and the --pager=yes logic into core. Only functionality change is that users now always get a --pager flag and can enable the pager via the flag without the extension active. Moving the flag into core exposes a defect in the ro localization, which will have to be corrected later.

pager: move pager-initiating code into core No functionality change. A previous version of this API had a category argument on ui.pager(). As I migrated the commands in core, I couldn't come up with good enough consistency in any categorization scheme so I just scrapped the whole idea. It may be worth revisiting in the future.

test-logtoprocess: use cat to wait for outputs Commands started by logtoprocess are running asynchronously. To be able to test the output, we need to block and wait for the output. The patch uses "| cat" to wait for such "asynchronous" outputs, to make the test more reliable. I have also written a short notice at the top, hopefully people would be aware of the pitfall when changing the test.

chgserver: move comments in config example "#" must be the first character of a line to mark the text as comments. So let's change the docstring.