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

test/functional/test_framework/script.py

@@ -28,6 +28,11 @@ MAX_PUBKEYS_PER_MULTI_A = 999
 LOCKTIME_THRESHOLD = 500000000
 ANNEX_TAG = 0x50
 
+SEQUENCE_LOCKTIME_DISABLE_FLAG = (1<<31)
+SEQUENCE_LOCKTIME_TYPE_FLAG = (1<<22) # this means use time (0 means height)
+SEQUENCE_LOCKTIME_GRANULARITY = 9 # this is a bit-shift
+SEQUENCE_LOCKTIME_MASK = 0x0000ffff
+
 LEAF_VERSION_TAPSCRIPT = 0xc0
 
 def hash160(s):