workflows: add MacOS 14 runner for tests

It's ARM-based, so it's a very nice combination.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

.github/workflows/tests.yml

@@ -120,7 +120,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-2022, macos-12]
+        os: [ubuntu-20.04, windows-2022, macos-12, macos-14]
         go_versions: [ '1.19', '1.20', '1.21' ]
         exclude:
           # Only latest Go version for Windows and MacOS.
@@ -132,6 +132,10 @@ jobs:
             go_versions: '1.19'
           - os: macos-12
             go_versions: '1.20'
+          - os: macos-14
+            go_versions: '1.19'
+          - os: macos-14
+            go_versions: '1.20'
           # Exclude latest Go version for Ubuntu as Coverage uses it.
           - os: ubuntu-20.04
             go_versions: '1.21'