gh-134531: cleanup `_hashopenssl.c` to support `EVP_MAC` (#134626)

gh-134531: cleanup `_hashopenssl.c` to support `EVP_MAC` (#134626)

Rename components related to `_hashlib.{HASH,HASHXOF}` objects.

- The `EVPobject` structure is renamed `HASHobject`.
- Non-clinic `HASH` methods are now prefixed by `_hashlib_HASH_*`.
  A similar change is made for non-clinic `HASHXOF` methods.
- Functions extracting information from `EVP_MD` objects and functions
  constructing `EVP_MD` objects now include `openssl_evp_md` in their name.

This change allows us to avoid future ambiguities between the `EVP_MD`
and the `EVP_MAC` APIs (currently, we only use `EVP_MD` for hash functions
and rely on the legacy interface for HMAC instead of using `EVP_MAC`).