Improve the readability and reduce brittleness of Variable Services "bucket" logic

[corthon]

You can see perhaps the worst offender here: https://github.com/microsoft/mu_basecore/blob/c4d0d1130454b3e5051bb601c707234e3a91713a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c#L2185

But the idea is to wrap each of these tests in a descriptive macro or function so that it's more readable AND we don't have to change multiple places if we ever change the logic (like adding a new PCD).

Example: WillVarExceedHwErrQuota( VarSize );, or something like that.

[github-actions[bot]]

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