rpc: clarify wrong-network address errors #35075

Fixes #26290.

This updates RPC address validation to return a more specific error when an address is valid for a different network than the one the node is running on.

Changes:

• add a shared helper to detect different-network addresses
• use it in generatetoaddress
• use it in the raw-address fallback path of generateblock
• use it for changeAddress / change_address in walletcreatefundedpsbt
• keep existing generic errors for malformed addresses

Tests:

• test/functional/rpc_generate.py
• test/functional/rpc_psbt.py

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #34950 (rpc: migrate generatetoaddress params to self.Arg for consistency by defenwycke)
• #32468 (rpc: generateblock to allow multiple outputs by polespinasa)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

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Concept NACK.

From a quick look at #27260(https://github.com/bitcoin/bitcoin/pull/27260), it seems to sufficiently address this issue. If you prefer a different approach, it would be helpful to explain why it’s better.

Thanks, that's helpful. I took a closer look at #27260 and agree this would duplicate that effort, so I'll close this one.