Fix T87967: M2T video seeking is broken

Bug caused by integer overflow in ffmpeg_generic_seek_workaround().
Function max_ii() was used to limit int_64tvalue.

After fixing the issue there was another issue, where near-infinite loop
was caused by requested_pos being very large and stream being cut in a
way, that it was missing keyframe at beginning.
This was fixed by checking if we are reading beyond file content.

Reviewed By: zeddb

Differential Revision: https://developer.blender.org/D11888

VSE: Use lines to draw waveform

Refactor and improve waveform drawing.

Drawing now can use line strips to draw waveforms instead of only
triangle strips. This makes us able to properly visualize thin waveforms
as they would not be visible before. We now also draw the RMS value of
the waveform.

The waveform drawing is now also properly aligned to the screen pixels
to avoid flickering when transforming the strip.

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11184

VSE: Fix audaspace not reading ffmpeg files with start offset correctly

The duration and start time for audio strips were not correctly read in
audaspace.

Some video files have a "lead in" section of audio that plays before the
video starts playing back. Before this patch, we would play this lead in
audio at the same time as the video started and thus the audio would not
be in sync anymore.

Now the lead in audio is cut off and the duration should be correctly
calculated with this in mind.

If the audio starts after the video, the audio strip is shifted to
account for this, but it will also lead to cut off audio which might not
be wanted. However we don't have a simple way to solve this at this
point.

Differential Revision: https://developer.blender.org/D11917

VSE: Fix seeking issues.

The seek pts was not correctly calculated.
In addition to that we were not seeking in the video pts time base.

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11921

VSE: Fix video strip duration calculation

The video duration was not read correctly from the video file.

It would use the global duration of the file which does in some cases
not line up with the actual duration of the video stream.
Now we take the video stream duration and start time into account when
calculating the strip duration.

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11920

VSE: Fix memory leak when adding bad image/movie strips

If the add strip operator errored out, we wouldn't free custom data allocated

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11919

VSE: Fix "off by one" error when encoding audio

Before we didn't encode the audio up until the current frame.
This lead to us not encoding the last video frame of audio.

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11918

VSE: Flush audio encode after finishing video export

We didn't flush audio after encoding finished which lead to audio
packets being lost.

In addition to this the audio timestamps were wrong because we
incremented the current audio time before using it.

Reviewed By: Richard Antalik

Differential Revision: https://developer.blender.org/D11916