When changing the target for display or window capture, force a
refresh of the source by setting the timer to fire immediately. This
removes 1-3 seconds of "lag" before the new display or window is
visible and makes the UI feel more responsive.

Closes https://github.com/obsproject/obs-studio/issues/2322

obs-outputs: Various librtmp mbedtls fixes

Previously the assertion required the idx to be smaller than the number
of elements in the darray. This would mean you could not insert anything
at the end of a darray, and would make it impossible to insert an array
into an empty darray.

This param is the buffer size, including null terminator

The last parameter is the buffer size (which would include null
terminator), not the desired string length.

obs-transitions: Halve stinger padding to 250ms

Triggering a new transition too soon after a
stinger would cause the wrong scene to be displayed

libobs: Add media control support to backend

media-playback: Add functions to pause/seek media source

UI: Use input validator on resolution line edit

UI: Fix transtions not enabled

The report in https://github.com/obsproject/obs-studio/issues/2350
identified the issue as being caused by mbedtls not following symbolic
links, but it turns out the issue was the mbedtls_x509_crt_parse_path
return value which was already fixed in 4d89123c. So these changes are
no longer necessary.

Same as obs_scene_find_source but also searches groups within the scene.

UI: Fix crash when entering large resolutions

enc-amf: Update to latest

Set stinger media source's name

Fixes a crash when entering large resolutions, and also works as a minor
sanity check against bad resolution values.

UI: Fix aspect ratio triggering settings change

Add support for MIPS architecture

This code is very old and seems to be non-functional in its current
state. The TLS support is also complicated to maintain across multiple
deprecated mbedtls functions.

Compilation with older versions of mbedtls was broken by
https://github.com/obsproject/obs-studio/pull/2304, unfortunately the
older version is still present in Ubuntu 16 LTS.

Though this should now be very rare, it's more helpful than "Failed to
connect to server". Other TLS error codes are now also stored for future
use instead of copying them on a case by case basis.

Errors or warnings in RTMP_Init were not copied to the OBS log file
if they occured before the callback was set.

Fixes https://github.com/obsproject/obs-studio/issues/2350. Also adds
some log file output for when the root certificates can't be loaded to
make it more obvious what the problem is.

Per mbedtls documentation, "If you share a context between threads, you
need to call these functions only from the main thread, at the beginning
and end of the context's lifetime.". OBS violated this since librtmp
uses a global context and it was allocated and freed in different
threads such as the auto config test.

This commit attaches the mbedtls context to an RTMP structure so there
is no more global state. It also fixes a rare double-free crash that
could occur if RTMP_TLS_Free was called twice (this happened in rare
situations such as the auto config running followed by a mode change
from Advanced to Simple).

libobs, obs-x264: Fix compiler warnings

UI: Fix t-bar not working with transition override

rtmp-services: Add Uscreen

Aarch64 and MIPS N64 ABI are safe to the uint to long cast.
Signed-off-by: NJiaxun Yang <jiaxun.yang@flygoat.com>