Fix Data.findFirstTypeMismatch to check all elements of Bundles

[jackkoenig]

Fix embarrassing bug introduced in #3201. Basically, DataMirror.checkTypeEquivalence is only checking the first element of Bundles 🙈

Fixes #3922

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Type of Improvement

• Bugfix

Desired Merge Strategy

• Squash

Release Notes

Fixes DataMirror.checkTypeEquivalence to actually check all fields of Bundles and Records. This may expose latent bugs in user code.

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[jackkoenig]

Turns out there were basically zero tests of this API. I did not write any for Const nor Probe which isn't great, but this needs to backport to 5.x.