Fix JSON operators

[simolus3]

This adds a new opt-in fix that updates how the JSON operators work. When opting in,

1. JSON paths that don't begin with $. are always interpreted as a single-element path (previously, we'd still split on . in the path).
2. When a null value is extracted via json_extract or ->>, fix the returned value to be null instead of "null". This fix also applies to elements extracted via json_each.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0a82f5c

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

This PR includes changesets to release 17 packages

Name	Type
@powersync/service-sync-rules	Minor
@powersync/service-image	Minor
@powersync/service-jpgwire	Patch
@powersync/service-core-tests	Patch
@powersync/service-core	Minor
@powersync/lib-services-framework	Patch
@powersync/service-module-mongodb-storage	Patch
@powersync/service-module-mongodb	Patch
@powersync/service-module-mysql	Patch
@powersync/service-module-postgres-storage	Patch
@powersync/service-module-postgres	Patch
@powersync/lib-service-postgres	Patch
@powersync/service-module-core	Patch
test-client	Patch
@powersync/service-rsocket-router	Patch
@powersync/lib-service-mongodb	Patch
@powersync/service-schema	Minor

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