refactor: Remove unused HaveKey and HaveWatchOnly #32476

1. 
   maflcko commented at 7:46 am on May 13, 2025: member

   removes some dead code
2. Remove HaveKey helper, unused after sethdseed removal fa7b7f796a
3. Remove unused LegacyDataSPKM::HaveWatchOnly() fabdc5ad06
4. 
   DrahtBot commented at 7:46 am on May 13, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32476.

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5. DrahtBot added the label Refactoring on May 13, 2025
6. 
   maflcko commented at 7:47 am on May 13, 2025: member

   (follow-up to #32438)
7. fanquake requested review from Sjors on May 13, 2025
8. 
   Sjors commented at 9:32 am on May 13, 2025: member

   utACK fabdc5ad06bce8cd3b0e525071d10f616a30bb04
9. fanquake merged this on May 13, 2025
10. fanquake closed this on May 13, 2025

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11. maflcko deleted the branch on May 13, 2025

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Refactoring