validatePayment does not settleUpTo toEpoch if in the same unproven period as fromPeriod

[wjmelements]

While this is intended behavior because we do not want to partial-settle into a period that may later be proven, endEpoch might not be in the current proving period. The logic should be changed to only settleUpTo fromEpoch if endEpoch is in the current proving period.

[wjmelements]

testValidatePayment_SomeEpochsProven seems to try to cover this case. I'll see why it doesn't.

[wjmelements]

testValidatePayment_SomeEpochsProven seems to try to cover this case. I'll see why it doesn't.

It proves periods 0 and 2 but not 1. We want a test that proves periods 1 and 2 but not 0.

[BigLep]

#foc-wg slack correspondence on this: https://filecoinproject.slack.com/archives/C08TVNKJV7C/p1770335766458709