Merge bitcoin/bitcoin#33135: wallet: warn against accidental unsafe older() import

76c092ff80 wallet: warn against accidental unsafe older() import (Sjors Provoost)
592157b759 test: move SEQUENCE_LOCKTIME flags to script (Sjors Provoost)

Pull request description:

  [BIP 379](https://github.com/bitcoin/bips/blob/master/bip-0379.md) ([Miniscript](https://bitcoin.sipa.be/miniscript/)) allows relative height and time locks that have no consensus meaning in [BIP 68](https://github.com/bitcoin/bips/blob/master/bip-0068.mediawiki) (relative timelocks) / [BIP 112](https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki) (`CHECKSEQUENCEVERIFY`). This is (ab)used by some protocols, e.g. [by Lightning to encode extra data](https://delvingbitcoin.org/t/exploring-extended-relative-timelocks/1818/23), but is unsafe when used unintentionally: `older(65536)` is equivalent to `older(1)`.

  This PR emits a warning when `importdescriptors` contains such a descriptor.

  The first commit makes `SEQUENCE_LOCKTIME` flags reusable by other tests.

  The main commit adds the `ForEachNode` helper to `miniscript.h` which is then used in the `MiniscriptDescriptor` constructor to check for `Fragment::OLDER` with unsafe values. These are stored in `m_warnings`, which the RPC code then collects via `Warnings()`.

  It adds both a unit and functional test.

  ---

  A previous version of this PR prevented the import, unless the user opted in with an `unsafe` flag. It also used string parsing in the RPC code.

  ---

  Based on:
  - [x] https://github.com/bitcoin/bitcoin/pull/33914

ACKs for top commit:
  pythcoiner:
    reACK 76c092ff80
  achow101:
    ACK 76c092ff80
  rkrux:
    lgtm re-ACK 76c092ff80
  brunoerg:
    reACK 76c092ff80

Tree-SHA512: 8e944e499bd4a43cc27eeb889f262b499b9b07aa07610f4a415ccb4e34a9110f9946646f446a54ac5bf17494d8d96a89e4a1fa278385db9b950468f27283e17a

src/wallet/test/walletload_tests.cpp

@@ -35,6 +35,7 @@ public:
     std::optional<int64_t> MaxSatisfactionWeight(bool) const override { return {}; }
     std::optional<int64_t> MaxSatisfactionElems() const override { return {}; }
     void GetPubKeys(std::set<CPubKey>& pubkeys, std::set<CExtPubKey>& ext_pubs) const override {}
+    std::vector<std::string> Warnings() const override { return {}; }
 };
 
 BOOST_FIXTURE_TEST_CASE(wallet_load_descriptors, TestingSetup)