Merge bitcoin/bitcoin#33489: build: Drop support for EOL macOS 13

1aaaaa078b fuzz: Drop unused workaround after Apple-Clang bump (MarcoFalke)
fadad7a494 Drop support for EOL macOS 13 (MarcoFalke)

Pull request description:

  Now that macOS 13 is EOL (https://en.wikipedia.org/wiki/MacOS_Ventura), it seems odd to still support it.

  (macOS Ventura 13.7.8 received its final security update on 20 Aug 2025: https://support.apple.com/en-us/100100)

  This patch will only be released in version 31.x, another 6 months out from now.

  So:

  * Update the depends build and release note template to drop EOL macOS 13.
  * As a result, update the earliest Xcode to version 16 in CI.
  * Also, bump the macOS CI runner to version 15, to avoid issues when version 14 will be at its EOL in about 1 year.

  This also allows to drop a small workaround in the fuzz tests and unlocks libcpp hardening (https://github.com/bitcoin/bitcoin/pull/33462)

ACKs for top commit:
  stickies-v:
    re-ACK 1aaaaa078b
  l0rinc:
    code review ACK 1aaaaa078b
  hodlinator:
    re-ACK 1aaaaa078b
  hebasto:
    ACK 1aaaaa078b.

Tree-SHA512: 6d247a8432ef8ea8c6ff2a221472b278f8344346b172980299507f9898bb9e8e16480c128b1f4ca692bcbcc393da2b2fd6895ac5f118bc09e0f30f910529d20c

doc/release-notes-empty-template.md

@@ -36,7 +36,7 @@ Compatibility
 ==============
 
 Bitcoin Core is supported and tested on operating systems using the
-Linux Kernel 3.17+, macOS 13+, and Windows 10+. Bitcoin
+Linux Kernel 3.17+, macOS 14+, and Windows 10+. Bitcoin
 Core should also work on most other Unix-like systems but is not as
 frequently tested on them. It is not recommended to use Bitcoin Core on
 unsupported systems.