Changes

saip: rework file sizes for "half-defined" template files

Define the file size early if possible.
Some templates (e.g. for 5GS) define files which aren't completely defined.
Fixes the parsing for 5GS SUCI_Calc_Info which doesn't have a file size defined.

The saip-tool will other crash when reading a 5G enabled profile:
```
Traceback (most recent call last):
  File "./contrib/saip-tool.py", line 458, in <module>
    pes = ProfileElementSequence.from_der(f.read())
  File "pySim/esim/saip/__init__.py", line 1679, in from_der
    inst.parse_der(der)
    ~~~~~~~~~~~~~~^^^^^
  File "pySim/esim/saip/__init__.py", line 1552, in parse_der
    self.pe_list.append(ProfileElement.from_der(first_tlv, pe_sequence=self))
                        ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "pySim/esim/saip/__init__.py", line 557, in from_der
    inst._post_decode()
    ~~~~~~~~~~~~~~~~~^^
  File "pySim/esim/saip/__init__.py", line 668, in _post_decode
    self.pe2files()
    ~~~~~~~~~~~~~^^
  File "pySim/esim/saip/__init__.py", line 655, in pe2files
    file = File(k, v, template.files_by_pename.get(k, None))
  File "pySim/esim/saip/__init__.py", line 133, in __init__
    self.from_tuples(l)
    ~~~~~~~~~~~~~~~~^^^
  File "pySim/esim/saip/__init__.py", line 358, in from_tuples
    self._body = self.file_content_from_tuples(l)
                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
  File "pySim/esim/saip/__init__.py", line 393, in file_content_from_tuples
    stream.write(self.template.expand_default_value_pattern(self.file_size))
                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "pySim/esim/saip/templates.py", line 123, in expand_default_value_pattern
    raise ValueError("%s does not have a default length" % self)
ValueError: FileTemplate(EF.SUCI_Calc_Info) does not have a default length
```

Change-Id: I7c4a0914aef1049a416e6b091f23daab39a1dd9c