Remove legacy vendor-prefixed DOM APIs and fallbacks

[sbc100]

Remove references to mozRequestFullScreen, msRequestFullscreen,
mozCancelFullScreen, msExitFullscreen, cancelFullScreen,
mozfullscreenchange, and MSFullscreenChange across libbrowser.js
and libglfw.js. Convert bracket notation
(canvasContainer['requestFullscreen'], document['exitFullscreen'])
to standard dot notation.

In libhtml5.js, remove document.mozFullScreenElement,
document.webkitCurrentFullScreenElement, and
document.msFullscreenElement from $getFullscreenElement(), leaving
document.fullscreenElement and document.webkitFullscreenElement
(guarded by MIN_SAFARI_VERSION). Also remove
screen.mozLockOrientation, screen.webkitLockOrientation,
screen.mozUnlockOrientation, and screen.webkitUnlockOrientation
from emscripten_lock_orientation and emscripten_unlock_orientation.

In libbrowser.js, libopenal.js, and closure-externs.js, remove
obsolete mozGetUserMedia, msGetUserMedia, and webkitGetUserMedia
fallbacks and extern definitions, and transition getUserMedia calls
from the deprecated callback API (navigator.getUserMedia) to standard
Promise-based navigator.mediaDevices.getUserMedia.

These prefixed properties and fallbacks are safe to remove because:

1. Fullscreen, Screen Orientation, and MediaDevices APIs became
   unprefixed standards across Firefox, Chrome, and Safari years ago
   (e.g. requestFullscreen in Firefox 64 / Chrome 71,
   navigator.mediaDevices.getUserMedia in Chrome 53 / Firefox 38 / Safari
   11). Emscripten's minimum supported browser versions
   (MIN_FIREFOX_VERSION = 79, MIN_CHROME_VERSION = 85) are well beyond
   when these unprefixed properties and methods became standard across
   major engines.
2. IE and legacy Edge (ms prefix) and Firefox OS (moz prefixes) are
   no longer supported.
3. Safari < 16.4 still requires webkit prefixes for Fullscreen, so
   webkitRequestFullscreen, webkitExitFullscreen,
   webkitfullscreenchange, and webkitFullscreenElement are retained
   where appropriate.

[sbc100]

I you prefer I could split this up like I did with #27341, #27339, #27338, #27340. This change seems fairly reasonable as is though.

[sbc100]

I updated the webkitRequestFullscreen usage to apply only for safari < 16.4

[kripken]

lgtm though I would still recommend manual testing here, ideally including safari, but even without, I don't think we have automatic tests that actually verify fullscreen works.

[sbc100]

I think @juj runs the whole browser test suite on Safari. We don't do any in our CI I'm afraid, although we arguably should do at least some!

To really test this change we would need to test to also test on safari older then 16.4.

I will manually test chrome and ff interactive full screen tests.

[sbc100]

I tested locally with chrome and firefox using interactive.test_html5_fullscreen and interactive.test_html5_emscripten_exit_fullscreen