[ktx] update to 4.3.0

[Zingam]

Library name

KTX-Software

New version number

4.3.0

Other information that may be useful (release notes, etc...)

Please update KTX-Software to version 4.3.0. It looks that is has some tool changes, so the update won't be trivial:

https://github.com/KhronosGroup/KTX-Software/releases/tag/v4.3.0-alpha3

Also why is necessary to patch the library. Could it be avoided, which will make updating ports easier?

KhronosGroup/KTX-Software#632

[Zingam]

#29756
#24620
#26923
#24869