Primary cache: don't denormalize defaulted component values

[teh-cmc]

The cache will now keep track of missing optional components, and store an empty slice instead of a bunch of None values.
When queried, an empty shows up as a None option to the end-user, who can act appropriately.

SFM before:

SFM after:

---

• Fixes Primary cache: don't denormalize defaulted values #4779
• DNR: requires Primary caching 19 (final): de-staticify cache globals #4856

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[github-actions]

Size changes

Name	cmc/primcache_19_statification	4891/merge	Change
JS	139.41 kiB	111.52 kiB	-20.01%

[jleibs]

Why do we need to insert/store anything? Can't we just return an empty container from the cache if the component-entry is missing when we try to access it?

[teh-cmc]

We need to keep track of the empty rows so all the component caches can share the same top-level offsets (similar to what we do in the store where we use a Option::<DataCell>::None value for that).

[jleibs]

Ahh, for the case of range-queries where only some of the rows are empty?

[teh-cmc]

Yep!