ToDo: use ISystemMediaTransportControls2

[clsid2]

This interface is not properly documented, so that is why it wasn't implemented before.

It can be used to set duration for SMTC and better handle seeking.

Example code from Firefox:
https://searchfox.org/mozilla-central/source/widget/windows/WindowsSMTCProvider.cpp
https://github.com/microsoft/win32metadata/blob/b07213e28bcc48221c155024f9c5e0e1a92c6497/generation/WinSDK/RecompiledIdlHeaders/winrt/windows.media.idl#L725-L745

Probably also needs us to upgrade from 8.1 to Windows 10 SDK.

Edit: it is defined in SDK 10.0.19041.0 which is a standard one from VS2019.

[adipose]

Possibly we can do it without the SDK using dll loads. If we drop 8.1 does it remove Win7 support?

[clsid2]

It should still support Win7SP1, so it will only drop Win7RTM support, which I am fine with, as that is a small group of users.

Ideally the SDK switch is done as a separate first step, after a release, to give it some testing time.

BE currently uses Windows SDK 10.0.22621.0
And I see a commit comment that 26100 should be avoided due to a x86 code generation bug.