IMA has the same behavior

Fixes #9240

… xbox (#9254)

### Summary
When playing a live HLS stream on Xbox, I was running into the following
error as soon as the playhead hit a discontinuity:

```
CHUNK_DEMUXER_ERROR_APPEND_FAILED: Sample encryption info is not available.
```

I noticed that [this
fix](#6719) was added
a while back to address this exact issue. A few months ago, [another
PR](#8210) was
submitted to abstract the feature detection logic, which I believe
unfortunately caused a regression.

The `requiresClearAndEncryptedInitSegments` helper was implemented in
both the Abstract Device and the Default Browser, but it looks like it
wasn't implemented in the Xbox class. This resulted in
`requiresClearAndEncryptedInitSegments` always returning false on that
platform (defaulting to the Abstract Device class's implementation,
which returns `false`).

This made the following logic (that fixed the
CHUNK_DEMUXER_ERROR_APPEND_FAILED error) fail:
```
if (device.requiresClearAndEncryptedInitSegments()) {
  const doubleInitSegment = new Uint8Array(initSegment.byteLength +
    modifiedInitSegment.byteLength);
  doubleInitSegment.set(modifiedInitSegment);
  doubleInitSegment.set(initSegment, modifiedInitSegment.byteLength);
  return doubleInitSegment;
}
```

### Fix
Overriding this function in the Xbox class fixes the problem. 

### Result
Playback now proceeds through HLS discontinuities on Xbox without
CHUNK_DEMUXER_ERROR_APPEND_FAILED.

…rc= (#9255)

Fixes #9253

Current ManifestFilterer logic checks all variants and throws
RESTRICTIONS_CANNOT_BE_MET if none of variants is playable. It's
redundant, because if at least one variant is playable, we will not emit
this error anyway, so we can quickly stop further processing if we
detect playable variant.

This fixes the bug where getThumbnails takes some time and the thumbnail
container is displayed in an incorrect position in the seekbar

During my tests I wasn't able to find a webOS TV which could handle
smooth codec switching properly. Let's disable it on all platform,
similar to what we've done on Tizen back in the day.

…ata (#9282)

As python v3 is now necessary in our build pipeline, use python3
explicitly in CI and tutorials, as not all OSes symlink `python` to
`python3`.

Since VR movement can be controlled with specific methods we should not
limit its use