{Packaging} Fix crash when another Python is installed on the system

The scripts are installed in <base>/Scripts, but PYTHONPATH was set to
<scripts>/src, although this directory doesn't even exist. I guess the
deployment used to be in src, but this is no longer the case.

Setting PYTHONPATH is done to avoid conflicts with other installations
of Python on the same machine. When it is set incorrectly, Python tend
to crash on startup (typically when loading incompatible ctypes).

Fixes Azure#28004, Azure#29630, Azure#30517, Azure#30536, Azure#30594, Azure#30700, Azure#30792.

src/azure-cli/az

@@ -3,7 +3,7 @@
 import sys
 import os
 
-dir = os.path.join(os.path.dirname(os.path.realpath(__file__)), 'src')
+dir = os.path.dirname(os.path.dirname(os.path.realpath(__file__)))
 
 if os.environ.get('PYTHONPATH') is None:
     os.environ['PYTHONPATH'] = dir

src/azure-cli/az.bat

@@ -1,11 +1,11 @@
 @echo off
 setlocal
 
-SET PYTHONPATH=%~dp0\src;%PYTHONPATH%
+SET PYTHONPATH=%~dp0\..;%PYTHONPATH%
 SET AZ_INSTALLER=PIP
 
-IF EXIST "%~dp0\python.exe" (
-  "%~dp0\python.exe" -m azure.cli %*
+IF EXIST "%~dp0\..\python.exe" (
+  "%~dp0\..\python.exe" -m azure.cli %*
 ) ELSE (
   python -m azure.cli %*
 )