Merge bitcoin/bitcoin#30272: doc: use TRUC instead of v3 and add release note

926b8e39dc [doc] add release note for TRUC (glozow)
19a9b90617 use version=3 instead of v3 in debug strings (glozow)
881fac8e60 scripted-diff: change names from V3 to TRUC (glozow)
a573dd2617 [doc] replace mentions of v3 with TRUC (glozow)
089b5757df rename mempool_accept_v3.py to mempool_truc.py (glozow)
f543852a89 rename policy/v3_policy.* to policy/truc_policy.* (glozow)

Pull request description:

  Adds a release note for TRUC policy which will be live in v28.0.

  For clarity, replaces mentions of "v3" with "TRUC" in most places. Suggested in
  - https://github.com/bitcoin/bitcoin/pull/29496#discussion_r1629749583
  - https://github.com/bitcoin/bitcoin/pull/29496#discussion_r1624500904

  I changed error strings from "v3-violation" to "TRUC-violation" but left v3 in the debug strings because I think it might be clearer for somebody who is debugging. Similarly, I left some variables unchanged because I think they're more descriptive this way, e.g. `tx_v3_from_v2_and_v3`. I'm happy to debate places that should or shouldn't be documented differently in this PR, whatever is clearest to everyone.

ACKs for top commit:
  instagibbs:
    reACK 926b8e39dc
  achow101:
    ACK 926b8e39dc
  ismaelsadeeq:
    Code review ACK 926b8e39dc

Tree-SHA512: 16c88add0a29dc6d1236c4d45f34a17b850f6727b231953cbd52eb9f7268d1d802563eadfc8b7928c94ed3d7a615275dd103e57e81439ebf3ba2b12efa1e42af

doc/release-notes-29496.md

@@ -0,0 +1,11 @@
+Mempool Policy Changes
+----------------------
+
+- Transactions with version number set to 3 are now treated as standard on all networks (#29496),
+  subject to Opt-in Topologically Restricted Until Confirmation (TRUC) Transactions policy as
+  described in [BIP 431](https://github.com/bitcoin/bips/blob/master/bip-0431.mediawiki).  The
+  policy includes limits on spending unconfirmed outputs (#28948), eviction of a previous descendant
+  if a more incentive-compatible one is submitted (#29306), and a maximum transaction size of 10,000vB
+  (#29873). These restrictions simplify the assessment of incentive compatibility of accepting or
+  replacing TRUC transactions, thus ensuring any replacements are more profitable for the node and
+  making fee-bumping more reliable.