Update ispc binary path on Windows, update civetweb to v1.16

[AhmedZero]

Type

• Bug fix (non-breaking change which fixes an issue): Fixes Cannot configure CMake on Windows 11 with Ninja generator. #5378

Motivation and Context

Checklist:

• I have run python util/check_style.py --apply to apply Open3D code style
  to my code.
• This PR changes Open3D behavior or adds new functionality.
  • Both C++ (Doxygen) and Python (Sphinx / Google style) documentation is
    updated accordingly.
  • I have added or updated C++ and / or Python unit tests OR included test
    results (e.g. screenshots or numbers) here.
• I will follow up and update the code if CI fails.
• For fork PRs, I have selected Allow edits from maintainers.

Description

solve ispc is not a full path to an existing compiler tool in Visual Studio 2022 and Windows 11

[update-docs]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[ssheorey]

Hi @AhmedZero, thanks for providing this bugfix! Can you talk about the civetweb upgrade? Is this related to the ispc issue?

Also the CI checks are not running, perhaps since the PR is not up to date with main. Can you update the PR with main ?

[AhmedZero]

I faced that error when build
civetweb/civetweb#1024
and resolved in new version of civetweb
I update the PR with main

[ssheorey]

Thanks @AhmedZero for the update.

Tested WebRTC (C++ and Python) visualization works with this PR after the civetweb update.