Change GCM to AES-GCM

[nnmkhang]

pub fn new(key: &[u8], cipher: BlockCipherType) -> Result<Self, SymCryptError> {

BlockCipherType can be multiple cipher types but currently only AES is supported for SymCrypt. Explore renaming to AES-GCM

[nnmkhang]

AesBlock should be renamed/removed

I would just call this Aes. AES is always a block cipher (although there are some block cipher modes that allow you to use them as stream ciphers).

[nnmkhang]

#45 (comment)