Use Enum with Tag for pretty repr

[Julien00859]

Hello there! First time contributing. I've tried to follow the contributing steps but couldn't make tox detect my pyenv config. I manually tested 2.7 and 3.10.

I was playing around with an interactive python and some x509 certificate, but I had to refer to the documentation every time I peeked at the next tag because I never remember the enumeration values.

So this PR makes printing a Tag prints the value from the enums, instead of some obscure integer:

Tag(nr=<Numbers.BitString: 0x03>, typ=<Types.Primitive: 0x00>, cls=<Classes.Universal: 0x00>)

Instead of

Tag(nr=3, typ=0, cls=0)

Note that in case of a non-universal class, it keeps the nr as as integer. If I understood it correctly, non-universal class are for user-defined types, so nr=1 isn't always a Numbers.Boolean right?

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I've tried different approach before settling on the one proposed here. Another of my attemps was to try and change the namedtuple for a collections.abc.Sequence to get control on the __init__ and __repr__. The code turned out too complicated due to the py2-compat.

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By the way, running the tox tests on the master branch yields some errors.

flake8 complains about the unused from numbers import Number import. sphinx complains that the https://tox.wiki/en/latest/install.html url is not found (HTTP 404). sphinx autodoc complains that the docstrings of asn1.Encoder.construct is broken.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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[andrivet]

Thank you for the PR. I will look at it.