Overhaul Engine singleton documentation

[Mickeon]

Continuation of similar past efforts with the same goal of refreshing the documentation up a notch. See also #80282 which is somewhat related.

This is particularly prickly due of the sheer size. There's also a constant fear of possibly losing important information, or making use of incorrect technical terms. A lot of the time is spent reading the original documentation and looking at the source code, too.

• Made the wording match how other classes are documented A LOT more closely;
  • Simplified some wording which may be seen as awkward to read;
  • Use the present simple over future tense when applicable (will return -> returns);
  • Turned some long-winded sentences into notes at the end (and viceversa);
• Link to other methods and parameters more often;
• Tweak and add slightly more examples all around;
• Tweak the way some dictionary entries are described:
  • There was this odd extra spacing after every entry and its description
    ([code]founders[/code] - Array of Strings, founder names).
    I can only speculate that documentation in the past used a fixed font spacing, which not longer matters, as it is stripped in the online documentation and just looks odd in the built-in one.
  • Add "- " prefixes. This turns them into proper list elements in the online documentation.
  • Add trailing semicolons at the end of every element.

---

Methods

get_architecture_name

• Add quotes around return values;
• Further clarify note below.

I still do not like "you can use the fact that" but it does work, I suppose?

get_author_info

• Shortened description considerably;
  • The previous description was oddly repetitive even though there was not much to describe. It's all in one paragraph now, at the cost of possibly being more difficult to translate(?).

get_copyright_info

• Detail how the parts entry of the dictionaries is composed;
  • The previous description did not give much insight on the most important values this method returns.

get_frames_per_second

• Slightly elaborate on the returned value;
  - "Returns the frames per second of the running game." wow, thanks!

get_license_info

• Detail returned key-values in the Dictionary.

get_main_loop

• Detail what the main loop is;
• Add note about the equivalent project setting.

get_singleton, has_singleton, get_singleton_list

• Remove possibly outdated example(?);
  - "e.g. GodotPayments." I can't even find anything concrete about it?
• Add note about Autoloads, which are not the same concept.

get_version_info

• Updated example to say 4.1.

I really do not like how this is described, but I don't know how to fix it right now.

get_write_movie_path

• Link to the equivalent project setting.

is_editor_hint

I feel like way more could be said here, but I don't know how to fix it right now.

is_in_physics_frame

• Add concrete example.

---

Properties

max_fps

• Completely overhaul description;

max_physics_steps_per_frame

Probably more should be done about it but I don't know how right now.

physics_jitter_fix

• Reordered description around.

physics_ticks_per_second

Probably more should be done about it but I don't know how right now.

print_error_messages

Probably more should be done about it but I don't know how right now.

time_scale

• Completely overhaul description;
• Add note about values below or equal to 0.

---

Feedback is very, very welcome. Especially right now. This class is huge and very technical.

[Mickeon]

Rebased after:

• Document AudioServer.playback_speed_scale in Engine.time_scale #86071

Would be nice for it to be looked at sooner than later.

[Mickeon]

Addressed the above feedback. Thank you very much.

[Mickeon]

Rebased and made a few more notable changes to read nicer, especially around get_version_info. Can we have this now by 4.3?

[mhilbrunner]

Besides the mentioned, this is looking good to me and can IMO be merged.

[adamscott]

Apart from the small typo, it seem really good. Definitely better than the previous version.

[akien-mga]

Thanks!