arm64 python: Avoid nested class in insn hook for 10x hook and 10% overall speedup (#2095)

* arm64 python: Avoid nested class in insn hook for 10x hook speedup

Promote CpReg to a module-level class to address unnecessary performance
reduction.  In a real-world use case tracing the emulation of real-world
machine code, this change reduces time spent in CpReg namedtuple
construction from 10% of overall time to below 1%, for a 10x speedup of
the insn hook itself, or a 10% overall speedup.  Measured using
cProfile, python 3.13.

* upgrade distro to 22.04

* revert to 22.04 for now

* also revert for wheels

---------

Co-authored-by: mio <mio@lazym.io>

.github/workflows/build-uc2.yml

@@ -471,7 +471,7 @@ jobs:
             generators: 'Ninja'
           }
           - {
-            os: ubuntu-latest,
+            os: ubuntu-22.04,
             arch: aarch64,
             python-arch: aarch64,
             python-ver: '3.8',
@@ -479,10 +479,10 @@ jobs:
             artifact: 'ubuntu-cmake-aarch64.7z',
             archiver: '7z a',
             generators: 'Ninja',
-            distro: ubuntu20.04
+            distro: ubuntu22.04
           }
           - {
-            os: ubuntu-latest,
+            os: ubuntu-22.04,
             arch: ppc64le,
             python-arch: ppc,
             python-ver: '3.8',
@@ -490,7 +490,7 @@ jobs:
             artifact: 'ubuntu-cmake-ppc64le.7z',
             archiver: '7z a',
             generators: 'Ninja',
-            distro: ubuntu20.04
+            distro: ubuntu22.04
           }
         compiler: [ gcc ]
     steps: