Move the conversion of `minimalInterval` to milliseconds to be grouped with the other time conversions from seconds to milliseconds.
This fixes a bug in which the minimal and main intervals were compared after the former had been converted to milliseconds but the latter had not. This could cause the heatbeat interval to blow out to unexpectedly high values if the minimal interval was set.
Props tabrisrp, sabernhardt, SergeyBiryukov, audrasjb.
Fixes#54825.
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