Changes

setup.py: install esim.asn1 resources, install esim.saip

These changes are necessary to successfully run
./tests/unittests/test_esim_saip.py with a pySim installed via
'pip install'.

For example:

   virtualenv venv
   source venv/bin/activate
   git clone ssh://gerrit.osmocom.org:29418/pysim
   pip install pysim/
   cd pysim
   ./tests/unittests/test_esim_saip.py

Before this patch, that would result first in package pySim.esim.saip being unknown
(not installed at all), and when that is added to setup.py, in this error:

	Traceback (most recent call last):
	  File "/home/moi/osmo-dev/src/pysim/tests/unittests/./test_esim_saip.py", line 23, in <module>
	    from pySim.esim.saip import *
	  File "/home/moi/s/esim/sysmo_esim_mgr/venv/lib/python3.13/site-packages/pySim/esim/saip/__init__.py", line 41, in <module>
	    asn1 = compile_asn1_subdir('saip')
	  File "/home/moi/s/esim/sysmo_esim_mgr/venv/lib/python3.13/site-packages/pySim/esim/__init__.py", line 56, in compile_asn1_subdir
	    for i in resources.files('pySim.esim').joinpath('asn1').joinpath(subdir_name).iterdir():
		     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
	  File "/usr/lib/python3.13/pathlib/_local.py", line 577, in iterdir
	    with os.scandir(root_dir) as scandir_it:
		 ~~~~~~~~~~^^^^^^^^^^
	FileNotFoundError: [Errno 2] No such file or directory: '/home/moi/s/esim/sysmo_esim_mgr/venv/lib/python3.13/site-packages/pySim/esim/asn1/saip'

After this patch, the test completes successfully.

	......
	----------------------------------------------------------------------
	Ran 6 tests in 0.067s

	OK

Related: sysmocom's eSIM manager product that is currently in
development needs to fully use pySim.esim.saip, ideally from a regular
'pip install', and not from using the pySim source tree directly.

Related: SYS#6768
Change-Id: I0d7d6962a308eccca589a42c22546d508ff686f5