Runtime: estimate dataclip size at the end of each step and throw if too large

[josephjclark]

use ensurePayloadSize to guesstimate whether the state object is too big, and throw a controlled error to tell users that their state object is too large

Data clip limit is a % of run memory (maybe 25%?) or a fixed size. Or maybe the value is like 25% vs 200mb

See #1203

[josephjclark]

Done in #1209