Added time utilities, TC time functions, and fixed up Lua sphinx docs

[XHawk87]

Closes #2796

common tests:

lua cmd log.debug("%s", time.now())
lua cmd log.debug("%s", time.to_iso8601_datetime(time.now()))
lua cmd log.debug("%s", time.to_iso8601_duration(99999))
lua cmd log.debug("%s", game.next_turn_change())
lua cmd log.debug("%s", game.last_turn_change())

server-side tests:

lua cmd log.debug("%s", game.seconds_since_turn_change())
lua cmd log.debug("%s", game.seconds_to_turn_change())

client-side tests:

chat.msg("%s", game.seconds_since_turn_change())
chat.msg("%s", game.seconds_to_turn_change())

[jwrober]

Some things I noticed at first glance.

You can use clang-tidy to check the header includes. Compile with the clang preset and then run clang-tidy path/to/.h,.cpp -p build-clang/ --checks="-*,misc-include-cleaner"

[jwrober]

Not related to this PR specifically, but I think I may have broken OBS integration. The CI didn't run here. @XHawk87 I assume you created this branch from recent master at least after commit hash 73c0d80453e59904adefc3da48344daf34135ad2?

[XHawk87]

Some things I noticed at first glance.

You can use clang-tidy to check the header includes. Compile with the clang preset and then run clang-tidy path/to/.h,.cpp -p build-clang/ --checks="-*,misc-include-cleaner"

How would I do this using the nix flake or docker? I can't build it directly on my OS.

[XHawk87]

Not related to this PR specifically, but I think I may have broken OBS integration. The CI didn't run here. @XHawk87 I assume you created this branch from recent master at least after commit hash 73c0d80453e59904adefc3da48344daf34135ad2?

It was rebased just before the PR.

[jwrober]

Some things I noticed at first glance.
You can use clang-tidy to check the header includes. Compile with the clang preset and then run clang-tidy path/to/.h,.cpp -p build-clang/ --checks="-*,misc-include-cleaner"

How would I do this using the nix flake or docker? I can't build it directly on my OS.

Ok. I'll do a clang-tidy check this evening on my local to double check.

[XHawk87]

I suspect that this fix to the ruleset and cli tests won't work cross platform because there won't be a runuser command to switch to the freeciv21 user. Might have to roll back those until we can think of a better way to do it.