[DRAFT] Clean up outdated signing code

[ValuedMammal]

Changed

• descriptor: Changed ExtractPolicy trait by removing signers param
• removed sign_options param from Wallet::finalize_psbt
• export: FullyNodedExport no longer exports private keys

Removed Wallet APIs

• set_keymap{s}
• get_signers
• add_signer
• sign

TODO

• Remove unused Create/Load params (keymap, extract_keys)
• Remove unused tests

[coveralls]

Pull Request Test Coverage Report for Build 17101740297

Details

• 68 of 84 (80.95%) changed or added relevant lines in 3 files are covered.
• 81 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-1.2%) to 83.692%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
wallet/src/wallet/mod.rs	12	15	80.0%
wallet/src/descriptor/policy.rs	47	60	78.33%

Files with Coverage Reduction	New Missed Lines	%
wallet/src/descriptor/mod.rs	2	88.0%
wallet/src/descriptor/policy.rs	3	78.37%
wallet/src/test_utils.rs	3	97.07%
wallet/src/wallet/utils.rs	6	91.3%
wallet/src/wallet/params.rs	7	72.38%
wallet/src/wallet/tx_builder.rs	9	91.93%
wallet/src/wallet/mod.rs	51	77.2%

Totals
Change from base Build 17053101419:	-1.2%
Covered Lines:	5994
Relevant Lines:	7162

---

💛 - Coveralls

[oleonardolima]

There isn't much difference from what's done in #235 and oleonardolima@e9f6b0a, except for the removal of the signers module (which I kept initially to maintain wallet tests, rather than using #[ignore]) and pinning examples to a specific version.

To make the upgrade for our users more straightforward and with a specific path, I think we should first deprecate the signing APIs (and possibly the policy too) in a forthcoming release and then remove them by #235 or this one.