Fixes #38662, update `imgui` to 1.90.6, update `vsgimgui` to 0.3.0.

imgui
-
Except `osx-binding, metal-binding, android-binding`, other features are
tested successfully in the following triplet:
```
x64-windows
x64-windows-static
```

Except `osx-binding,metal-binding,android-binding,dx12-binding`, other
features are tested successfully in the following triplet:
```
x86-windows
```

- [x] Changes comply with the [maintainer
guide](https://github.com/microsoft/vcpkg-docs/blob/main/vcpkg/contributing/maintainer-guide.md).
- [x] SHA512s are updated for each updated download.
- [ ] ~The "supports" clause reflects platforms that may be fixed by
this new version.~
- [ ] ~Any fixed [CI
baseline](https://github.com/microsoft/vcpkg/blob/master/scripts/ci.baseline.txt)
entries are removed from that file.~
- [ ] ~Any patches that are no longer applied are deleted from the
port's directory.~
- [x] The version database is fixed by rerunning `./vcpkg x-add-version
--all` and committing the result.
- [x] Only one version is added to each modified port's versions file.

---------

Co-authored-by: Monica <v-liumonica@microsoft.com>