feat!: Enable reading JSON data with dbjson extension dtype

[chelsea-lin]

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Fixes internal issue 377764399 🦕

[tswast]

Very cool!

Let's make sure we mark this as a "breaking change" in our release notes (https://github.com/googleapis/release-please/blob/main/README.md#how-should-i-write-my-commits)

Since it's a breaking change for a preview feature, we shouldn't bump to 2.0 though. Let's use the Release-As footer in the commit message to make sure we do a 1.x release. https://github.com/googleapis/release-please/blob/main/README.md#how-do-i-change-the-version-number