Merge bitcoin/bitcoin#24236: Remove utxo db upgrade code

fa9112aac0 Remove utxo db upgrade code (MarcoFalke)

Pull request description:

  It is not possible to upgrade Bitcoin Core pre-segwit (pre-0.13.1) to a recent version without a full IBD from scratch after  commit 19a56d1519 (released in version 22.0).

  Any Bitcoin Core version with the new database format after commit 1088b02f0c (released in version 0.15), can upgrade to any version that is supported as of today.

  This leaves the versions 0.13.1-0.14.x. Even though those versions are unsupported, some users with an existing datadir may want to upgrade to a recent version. However, it seems reasonable to simply ask them to `-reindex` to run a full IBD from scratch. This allows us to remove the utxo db upgrade code.

ACKs for top commit:
  Sjors:
    re-ACK fa9112aac0
  laanwj:
    Code review ACK fa9112aac0

Tree-SHA512: 4243bb35df9ac4892f9fad30fe486d338745952bcff4160bcb0937c772d57b13b800647da14695e21e3655e85ee0d95fa3dc7789ee309d59ad84f422297fecb8

test/functional/test_runner.py

@@ -306,6 +306,7 @@ BASE_SCRIPTS = [
     'p2p_ping.py',
     'rpc_scantxoutset.py',
     'feature_txindex_compatibility.py',
+    'feature_unsupported_utxo_db.py',
     'feature_logging.py',
     'feature_anchors.py',
     'feature_coinstatsindex.py',