Merge bitcoin/bitcoin#26716: ci: Build python from source in "lint" task

123043e99c ci: Bump lint task image to Ubuntu Jammy (Hennadii Stepanov)
9b86114058 ci: Use pyenv's `python-build` to install Python in lint task (Hennadii Stepanov)

Pull request description:

  This PR:
  - is an alternative to bitcoin/bitcoin#26581 and bitcoin/bitcoin#26637
  - closes bitcoin/bitcoin#26548

  Key advantages of this PR over others:
  - it uses pyenv's `python-build` [standalone](https://github.com/pyenv/pyenv/tree/master/plugins/python-build#using-python-build-standalone)
  - requires no additional computational resources

  Note for testing. The lint task must success regardless of whether the `python_cache` is populated or invalidated.

ACKs for top commit:
  MarcoFalke:
    ACK 123043e99c
  fanquake:
    ACK 123043e99c

Tree-SHA512: ba0fcdd4f2939a59692b173dcd1f5704444cfcfbb8111538c6f8160056d0536bba250e4f9b0f8c66f8b454e52034bf36ffe6afae76cdc0f7cc5b58b576d790ba

.cirrus.yml

@@ -65,14 +65,17 @@ compute_credits_template: &CREDITS_TEMPLATE
   use_compute_credits: $CIRRUS_REPO_FULL_NAME == 'bitcoin/bitcoin' && $CIRRUS_PR != ""
 
 task:
-  name: 'lint [bionic]'
+  name: 'lint [jammy]'
   << : *BASE_TEMPLATE
   container:
-    image: ubuntu:bionic  # For python 3.6, oldest supported version according to doc/dependencies.md
+    image: ubuntu:jammy
     cpu: 1
     memory: 1G
   # For faster CI feedback, immediately schedule the linters
   << : *CREDITS_TEMPLATE
+  python_cache:
+    folder: "/tmp/python"
+    fingerprint_script: cat .python-version /etc/os-release
   lint_script:
     - ./ci/lint_run_all.sh
   env: