FormLayout calls MinSize twice

[dweymouth]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

When #4821 was closed out FormLayout moved away from allocating in every MinSize/Layout call, but introduced new behavior that MinSize is called twice per object instead of once. We can do a small form optimization where a table is stack-allocated for small forms with less than say 16 rows, and the old algorithm can be used.

How to reproduce

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Screenshots

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Example code

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Fyne version

develop

Go compiler version

n/a

Operating system and version

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Additional Information

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