Add sample for separate image samplers

[SaschaWillems]

Description

This PR adds a basic api sample demonstrating how to separate images and samplers. This is similar to the LunarG sample from the archived repository.

The sample uses one image and two different samplers, one with linear and one with nearest filtering, which can be selected at runtime.

It also comes with a small tutorial/readme describing the relevant parts of the application and shader code and a small comparison with a combined setup.

The sample was tested on Windows 10 with an NVIDIA RTX 2060. It's based on the texture loading sample, so it should work any pretty much every platform.

Fixes #302

General Checklist:

Please ensure the following points are checked:

• My code follows the coding style
• I have reviewed file licenses
• I have updated the header Copyright to reflect the current year (CI build will fail if Copyright is out of date)
• I have commented any added functions (in line with Doxygen)
• I have commented any code that could be hard to understand
• My changes do not add any new compiler warnings
• My changes do not add any new validation layer errors or warnings
• I have used existing framework/helper functions where possible
• My changes build on Windows, Linux, macOS and Android. Otherwise I have documented any exceptions
• My changes do not add any regressions
• I have tested every sample to ensure everything runs correctly
• This PR describes the scope and expected impact of the changes I am making

Sample Checklist

If your PR contains a new or modified sample, these further checks must be carried out in addition to the General Checklist:

• I have tested the sample on at least one compliant Vulkan implementation
• If the sample is vendor-specific, I have tagged it appropriately
• I have stated on what implementation the sample has been tested so that others can test on different implementations and platforms
• Any dependent assets have been merged and published in downstream modules
• For new samples, I have added a paragraph with a summary to the appropriate chapter in the samples readme

[gpx1000]

small warning issues but otherwise looks good to me runs well here.

[gary-sweet]

Looks good to me