Support rollup and integer states state/timeline aggs

[syvb]

• Adds rollup for state_agg and timeline_agg.
• Supports integer states for state_agg and timeline_agg. An aggregate can have integer states or string states, but not both. For a few functions this would mean having two functions with the same argument types but differing return types, so in that case I made a separate function for integer-valued aggregates (e.g. state_int_timeline).

Ideally this should have been two separate PRs, but my changes to rollup and the rest of the state_agg code have become intertwined.

(this should be merged after #636)

[WireBaron]

I believe the inputs to the trans function all below to the aggregate context so shouldn't need to be cloned.

[syvb]

bors r+

[bors]

Build succeeded:

• Clippy/rustfmt Test
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• Test Postgres (13)
• Test Postgres (14)