[OpenEXR] Update to v2.3.0

[cenit]

Upgrade the whole package:

• move to github
• update to v2.3.0
• improve the FindOpenEXR.cmake, maintaining backwards compatibility (there's an official one distributed with the package but it is completely different, for now it is avoided)
• remove the ilmbase port because now it is part of OpenEXR
• enable installation of OpenEXR tools

[UnaNancyOwen]

[x] remove the ilmbase port because now it is part of OpenEXR

I agree. I think it is a good proposal than my pull request #4820. 👍
@ras0219-msft What do you think?

[cenit]

I just updated freeimage to comply with the new OpenEXR.
I noticed that also updates to alembic and to OpenVDB may be necessary, due to this upgrade...

edit: no update is necessary to alembic

[cenit]

this PR is necessary to build #5169 with all features

[vicroms]

@cenit
Shouldn't OpenEXR be disabled for UWP? The now removed port for ilmbase didn't support UWP, and now that it is embedded into OpenEXR doesn't the same restriction apply?

[cenit]

you're right, there's a failure in ilmbase due to getenv and strerror function usage.
Sorry I didn't check all the ports with all the triplets, CI would be great to be exposed ;)
I am going to fix it asap

[vicroms]

Great. I made a few changes so that OpenEXR can be built on Linux and MacOS, for now those changes are only on my branch.

I also pulled your changes to openvdb (PR #5265) as the removal of ilmbase would cause regressions otherwise, the CI build takes a while to finish, but hopefully this time it is successful.

[cenit]

closed in favor of #5417