ext/sodium: revert addition of extendable output functions

The extendable output functions treated the state as a string, rather than an
opaque object, and only validated the lengths of the strings before converting
them to the underlying libsodium objects. Thus, incorrect state values could be
used to trigger out of bounds reads or updates.

The following constants are removed:

- `SODIUM_CRYPTO_XOF_SHAKE128_BLOCKBYTES`
- `SODIUM_CRYPTO_XOF_SHAKE128_STATEBYTES`
- `SODIUM_CRYPTO_XOF_SHAKE256_BLOCKBYTES`
- `SODIUM_CRYPTO_XOF_SHAKE256_STATEBYTES`
- `SODIUM_CRYPTO_XOF_TURBOSHAKE128_BLOCKBYTES`
- `SODIUM_CRYPTO_XOF_TURBOSHAKE128_STATEBYTES`
- `SODIUM_CRYPTO_XOF_TURBOSHAKE256_BLOCKBYTES`
- `SODIUM_CRYPTO_XOF_TURBOSHAKE256_STATEBYTES`

The following functions are removed:

- `sodium_crypto_xof_shake128()`
- `sodium_crypto_xof_shake128_init()`
- `sodium_crypto_xof_shake128_update()`
- `sodium_crypto_xof_shake128_squeeze()`
- `sodium_crypto_xof_shake256()`
- `sodium_crypto_xof_shake256_init()`
- `sodium_crypto_xof_shake256_update()`
- `sodium_crypto_xof_shake256_squeeze()`
- `sodium_crypto_xof_turboshake128()`
- `sodium_crypto_xof_turboshake128_init()`
- `sodium_crypto_xof_turboshake128_update()`
- `sodium_crypto_xof_turboshake128_squeeze()`
- `sodium_crypto_xof_turboshake256()`
- `sodium_crypto_xof_turboshake256_init()`
- `sodium_crypto_xof_turboshake256_update()`
- `sodium_crypto_xof_turboshake256_squeeze()`

Author: DanielEScherzer