Add 2.5 second timeout for AMF test process

[notr1ch]

Description

Adds a 2.5 second timeout to the enc-amf-test on Windows, after which point the process self-terminates.

Motivation and Context

Some users report the OBS UI failing to appear despite obs64.exe running. In one case, this was caused by the AMF test executable freezing, and OBS waiting forever on a pipe ReadFile call. Self-terminating the test executable seemed like an easier implementation than asynchronous pipe I/O and has the benefit of cleaning up the frozen process.

Yes, it is a bit hacky, but AMF is long overdue for a rewrite anyway.

Ref: https://github.com/obsproject/obs-studio/issues/6230

How Has This Been Tested?

Ran enc-amf-test with hardcoded delays and verified it terminated and OBS reported a timeout.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.

[RytoEX]

Any reason not to use "Fixes #6230"?

[notr1ch]

I wasn't sure that worked across repositories.

[RytoEX]

You can leave it for a submodule update commit if you prefer.

[vivi90]

pls merge