[Ledgers] Add the remaining built-in Ledger kinds #37593

Adds the remaining built-in Ledger kinds.

Ledgers are limited to a fixed set of built-in kinds. There is no generic Ledger constructor, by design. We could consider adding one later if a compelling use case arises.

All the built-in kinds follow certain algebraic properties:

• Monotonicity. A write in one component must not cancel out a write in a different component. For example, once a bit is set in a Mask ledger, it can never be unset.


• Commutativity. The order of writes should not affect the final total. This allows us to stream parallel parts of the graph independently, without buffering them to preserve write order.


• Associativity. Grouping writes into partial totals must not affect the final total. This allows us to accumulate and merge totals incrementally. If a stream is intentionally closed early during partial prerendering, its total describes the portion that was received.

The built-in Ledger kinds are:

• 
  createBitLedger. Flips a flag from false to true.


• 
  createMaskLedger. Adds bits to a bitmask.


• 
  createMinLedger. Tracks the smallest number.


• 
  createMaxLedger. Tracks the largest number.


• 
  createSetLedger. Accumulates a Set of scalar values.

There's a caveat regarding Set Ledgers: Sets in JavaScript have an iteration order, but React does not guarantee anything about the order of the entries in the final Set. The order is considered undefined and consumers must not rely on it.

Sets also only support scalar values for now, not objects. This is because object identity is not a good basis for set equality. We may add support for sets of arbitrary values later, though we'll need to consider the identity question again.