zcash_client_sqlite: Backport PIR spent-note tracking to 0.19.x#2268

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zcash:maint/zcash_client_sqlite-0.19.xzcash/librustzcash:maint/zcash_client_sqlite-0.19.xfrom

p0mvn:sync-pir-0.19.xp0mvn/librustzcash:sync-pir-0.19.xCopy head branch name to clipboard