Remove deprecated host (mac12, ubuntu20) and set the min. python version to 3.8

Signed-off-by: Chin Yeung Li <tli@nexb.com>

Author: chinyeungli

azure-pipelines.yml

@@ -1,56 +1,38 @@
-
 ################################################################################
 # We use Azure to run the full tests suites on multiple Python 3.x
 # on multiple Windows, macOS and Linux versions all on 64 bits
 # These jobs are using VMs with Azure-provided Python builds
 ################################################################################
 
 jobs:
-
-    - template: etc/ci/azure-posix.yml
-      parameters:
-          job_name: ubuntu20_cpython
-          image_name: ubuntu-20.04
-          python_versions: ['3.7', '3.8', '3.9', '3.10', '3.11']
-          test_suites:
-              all: venv/bin/pytest -n 2 -vvs
-
     - template: etc/ci/azure-posix.yml
       parameters:
           job_name: ubuntu22_cpython
           image_name: ubuntu-22.04
-          python_versions: ['3.7', '3.8', '3.9', '3.10', '3.11']
-          test_suites:
-              all: venv/bin/pytest -n 2 -vvs
-
-    - template: etc/ci/azure-posix.yml
-      parameters:
-          job_name: macos12_cpython
-          image_name: macOS-12
-          python_versions: ['3.7', '3.8', '3.9', '3.10', '3.11']
+          python_versions: ['3.8', '3.9', '3.10', '3.11']
           test_suites:
               all: venv/bin/pytest -n 2 -vvs
 
     - template: etc/ci/azure-posix.yml
       parameters:
           job_name: macos13_cpython
           image_name: macOS-13
-          python_versions: ['3.7', '3.8', '3.9', '3.10', '3.11']
+          python_versions: ['3.8', '3.9', '3.10', '3.11']
           test_suites:
               all: venv/bin/pytest -n 2 -vvs
 
     - template: etc/ci/azure-win.yml
       parameters:
           job_name: win2019_cpython
           image_name: windows-2019
-          python_versions: ['3.7', '3.8', '3.9', '3.10', '3.11']
+          python_versions: ['3.8', '3.9', '3.10', '3.11']
           test_suites:
               all: venv\Scripts\pytest -n 2 -vvs
 
     - template: etc/ci/azure-win.yml
       parameters:
           job_name: win2022_cpython
           image_name: windows-2022
-          python_versions: ['3.7', '3.8', '3.9', '3.10', '3.11']
+          python_versions: ['3.8', '3.9', '3.10', '3.11']
           test_suites:
               all: venv\Scripts\pytest -n 2 -vvs