cbf2d75d8f49b7b1e32acb5373b312b484f3fa6a qa: Add getdescriptorinfo functional test (João Barbosa)
Pull request description:
The `getdescriptorinfo` RPC was added in #15368, this PR adds some tests.
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Tree-SHA512: 5bf3fb5842b975089821c7ac52202ecb23df255f655862646eb532e38e335ff963f8973bcf5b8bba386183281dc9bfe7279ba1cf25fd518c9a45fb45a9243e4d
