Newer version of mimaloc and removed unused function

[FilipNur]

Older version of mimalloc caused build errors.
IsHighIntegrity function was unused.

[ci-tester-lunarg]

Author FilipNur not on autobuild list. Waiting for curator authorization before starting CI build.

[CLAassistant]

All committers have signed the CLA.

[spencer-lunarg]

Older version of mimalloc caused build errors.

Can you explain more on this?

We have had issues with mimalloc upgrades in the past, so if we are going to upgrade it

1. It should be the only change (the IsHighIntegrity change is valid, but unrelated)
2. I want record of why we did it

[FilipNur]

@spencer-lunarg

1. The mimalloc repository had error when compiling it. The error was about implicit casting between different pointer types. The version that was used previously still had that error. The version that this pull request uses is the newest version of mimalloc as of this moment, and it does not have that or any other compilation errors.
2. During test compilation of this repo the warning about unused function came up, which was IsHighIntegrity. The VScode's search in all files did not find any other occurence of IsHighIntegrity other than the declaration of this function. If the function should stay in the code, or it's use is planned for the future, I will roll back the change that deletes it. If the IsHighIntegrity's code must stay in the source, then the warning about unused function can be suppressed by commenting out entire function.

[ci-tester-lunarg]

Author FilipNur not on autobuild list. Waiting for curator authorization before starting CI build.

[spencer-lunarg]

@FilipNur sorry, I messed up, didn't run this change through CI and it is blowing stuff up now, going to quick revert #13158 and unblock CI, will try updating again, will need to figure out what is wrong