RNG seeding updates, update default RNG to MT64

[WinterSolstice8]

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• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
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• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Improves RNG seeding with more secure methods
Switch to MT64 by default

Disables PCG32/64 due to imneme/pcg-cpp#94

This used to disable PCG32/64 but it turns out that's not a problem, the way we seed isn't effected

Steps to test these changes

compile, see RNG works with no errors