Fix issue with reducer initial state variable causing collisions due to variable references

[clauderic]

Fixes #46

The initial state variable was being shared across all <DndContext> components in the same application, which was causing id collisions for both nested and sibling <DndContext> providers.

See https://codesandbox.io/s/fervent-wing-0zqhd for a sandbox replicating this issue.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5194696

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@dnd-kit/core	Patch

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[github-actions]

Size Change: +70 B (0%)

Total Size: 62.5 kB

Filename	Size	Change
packages/core/dist/core.cjs.development.js	16.4 kB	+26 B (0%)
packages/core/dist/core.cjs.production.min.js	9.99 kB	+10 B (0%)
packages/core/dist/core.esm.js	16.2 kB	+34 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
packages/accessibility/dist/accessibility.cjs.development.js	979 B	0 B
packages/accessibility/dist/accessibility.cjs.production.min.js	637 B	0 B
packages/accessibility/dist/accessibility.esm.js	847 B	0 B
packages/accessibility/dist/index.js	148 B	0 B
packages/core/dist/index.js	141 B	0 B
packages/modifiers/dist/index.js	144 B	0 B
packages/modifiers/dist/modifiers.cjs.development.js	838 B	0 B
packages/modifiers/dist/modifiers.cjs.production.min.js	574 B	0 B
packages/modifiers/dist/modifiers.esm.js	766 B	0 B
packages/sortable/dist/index.js	144 B	0 B
packages/sortable/dist/sortable.cjs.development.js	3.96 kB	0 B
packages/sortable/dist/sortable.cjs.production.min.js	2.53 kB	0 B
packages/sortable/dist/sortable.esm.js	3.85 kB	0 B
packages/utilities/dist/index.js	144 B	0 B
packages/utilities/dist/utilities.cjs.development.js	1.63 kB	0 B
packages/utilities/dist/utilities.cjs.production.min.js	962 B	0 B
packages/utilities/dist/utilities.esm.js	1.55 kB	0 B

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