rpc: Fix `setwalletflag` disabling of flags #24855

1. 
   achow101 commented at 6:45 PM on April 14, 2022: member

   Trying to disable a wallet flag with setwalletflag results in Internal bug detected: 'std::any_of(m_results.m_results.begin(), m_results.m_results.end(), [ret](const RPCResult& res) { return res.MatchesType(ret); })'. This occurs because the warnings field was not marked as optional. This PR makes warnings optional to avoid this error.

   Also added a test case because apparently we didn't already have one.

2. rpc, wallet: setwalletflags warnings are optional

   Without this, trying to disable a wallet flag results in an Internal bug
   detected.

   17ab31aa46
3. test: Test for disabling wallet flags 88376c623c
4. fanquake added the label RPC/REST/ZMQ on Apr 14, 2022
5. MarcoFalke added this to the milestone 24.0 on Apr 15, 2022
6. 
   MarcoFalke commented at 7:22 AM on April 15, 2022: member

   ACK

   For context: #24695

7. w0xlt approved
8. 
   w0xlt commented at 7:18 AM on April 16, 2022: contributor

   ACK 88376c6

9. nina1234 approved
10. 
    nina1234 commented at 7:32 AM on April 16, 2022: none

    Hi

11. fanquake merged this on Apr 16, 2022
12. fanquake closed this on Apr 16, 2022

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13. sidhujag referenced this in commit 5e185e3a98 on Apr 18, 2022
14. luke-jr referenced this in commit 80c7687ff2 on May 21, 2022
15. luke-jr referenced this in commit 57fc792b74 on May 21, 2022
16. DrahtBot locked this on Apr 16, 2023

Milestone
24.0