Merge bitcoin/bitcoin#28211: Bump python minimum supported version to 3.9

fa25e8b0a1 doc: Recommend lint image build on every call (MarcoFalke)
faf70c1f33 Bump python minimum version to 3.9 (MarcoFalke)
fa8996b930 ci: Bump i686_multiprocess.sh to latest Ubuntu LTS (MarcoFalke)

Pull request description:

  All supported operating systems ship with python 3.9 (or later), so bumping the minimum should not cause any issues. A bump will allow new code to use new python 3.9 features.

  For reference:
  * https://packages.debian.org/bullseye/python3
  * https://packages.ubuntu.com/focal/python3.9
  * FreeBSD 12/13 also ships with 3.9
  * CentOS-like 8/9 also ships with 3.9 (and 3.11)
  * OpenSuse Leap also ships with 3.9 (and 3.11) https://software.opensuse.org/package/python311-base

  This is for Bitcoin Core 27.0 in 2024 (next year), not the soon upcoming 26.0 next month.

ACKs for top commit:
  Sjors:
    ACK fa25e8b0a1
  jamesob:
    ACK fa25e8b0a1 ([`jamesob/ackr/28211.1.MarcoFalke.bump_python_minimum_supp`](https://github.com/jamesob/bitcoin/tree/ackr/28211.1.MarcoFalke.bump_python_minimum_supp))

Tree-SHA512: 86c9f6ac4b5ba94a62ee6a6062dd48a8295d8611a39cdb5829f4f0dbc77aaa1a51edccc7a99275bf699143ad3a6fe826de426d413e5a465e3b0e82b86d10c32e

doc/dependencies.md

@@ -10,7 +10,7 @@ You can find installation instructions in the `build-*.md` file for your platfor
 | [Automake](https://www.gnu.org/software/automake/) | [1.13](https://github.com/bitcoin/bitcoin/pull/18290) |
 | [Clang](https://clang.llvm.org) | [10.0](https://github.com/bitcoin/bitcoin/pull/27682) |
 | [GCC](https://gcc.gnu.org) | [9.1](https://github.com/bitcoin/bitcoin/pull/27662) |
-| [Python](https://www.python.org) (scripts, tests) | [3.8](https://github.com/bitcoin/bitcoin/pull/27483) |
+| [Python](https://www.python.org) (scripts, tests) | [3.9](https://github.com/bitcoin/bitcoin/pull/28211) |
 | [systemtap](https://sourceware.org/systemtap/) ([tracing](tracing.md))| N/A |
 
 ## Required