* support bitstring values in DNs

parsing is limited to x500UniqueIdentifier only

* Update src/cryptography/x509/name.py

Co-authored-by: Alex Gaynor <alex.gaynor@gmail.com>

Co-authored-by: Alex Gaynor <alex.gaynor@gmail.com>

The spec requires both of these to be exactly two characters to
correspond with ISO country codes. Reality is sometimes messier, so this
allows parsing (but not encoding) of this invalid data. Parsing will
raise a UserWarning if incorrect lengths are detected.

* Allow to serialize extension values as DER bytes string.

* Prepare test for SignedCertificateTimestamps.

also document that we can return these key types in a certificate,
although they can't be self-signed of course

* Move around some code to kill the need for a backend method
* Type the backend arg to typing.Any since we just don't care now

`rfc4514_string()` and related methods now have an optional
`attr_name_overrides` parameter to supply custom OID to name mappings,
which can be used to match vendor-specific extensions.

**BACKWARDS INCOMPATIBLE:** Reverted the nonstandard formatting of email
address fields as `E` in `rfc4514_string()` methods from version 35.0.

The previous behavior can be restored with:
`name.rfc4514_string({NameOID.EMAIL_ADDRESS: "E"})`

Expanded documentation of `Name.rfc4514_string`.

* Convert CRL creation to Rust

* fixes

* small reflows

* Delete all teh code

* flake8

* Convert CSR creation to Rust

* put this back

* unused

* coverage