Reduce updating frequency for fps in GUI.

[asuessenbach]

Description

Currently, the fps information in the GUI is hard to read, as it's changing to often. With this change, the fps is updated only after at least half a second.

Build tested on Win10 with VS2022. Run tested on Win10 with NVidia GPU.

General Checklist:

Please ensure the following points are checked:

• [x] My code follows the coding style
• [x] I have reviewed file licenses
• [x] I have commented any added functions (in line with Doxygen)
• [x] I have commented any code that could be hard to understand
• [x] My changes do not add any new compiler warnings
• [x] My changes do not add any new validation layer errors or warnings
• [x] I have used existing framework/helper functions where possible
• [x] My changes do not add any regressions
• [x] I have tested every sample to ensure everything runs correctly

• [x] This PR describes the scope and expected impact of the changes I am making

  Note: The Samples CI runs a number of checks including:

  • [x] I have updated the header Copyright to reflect the current year (CI build will fail if Copyright is out of date)
  • [ ] My changes build on Windows, Linux, macOS and Android. Otherwise I have documented any exceptions

  If this PR contains framework changes:

  • [ ] I did a full batch run using the batch command line argument to make sure all samples still work properly

Sample Checklist

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

• [x] I have tested the sample on at least one compliant Vulkan implementation
• [x] If the sample is vendor-specific, I have tagged it appropriately
• [x] I have stated on what implementation the sample has been tested so that others can test on different implementations and platforms
• [x] Any dependent assets have been merged and published in downstream modules
• [x] For new samples, I have added a paragraph with a summary to the appropriate chapter in the readme of the folder that the sample belongs to e.g. api samples readme
• [x] For new samples, I have added a tutorial README.md file to guide users through what they need to know to implement code using this feature. For example, see conditional_rendering
• [x] For new samples, I have added a link to the Antora navigation so that the sample will be listed at the Vulkan documentation site