[inorick]

Export changes from Google3

• Move engineSetPadding and block size implementations from OpenSSLCipher into its subclasses, and expand OpenSSLCipherTest (getBlockSize() and getOutputSize() tests).
• Improve EVP_HPKE_CTX setup error handling and native ref creation in NativeCrypto.
• Avoid using a function pointer in evpDigestSignVerifyInit for BoringSSL const-correctness compatibility.
• Restore Platform.isPqcKemKdfSupported() in the Android platform variant.
• Set project version in build.gradle back to 2.8-SNAPSHOT and update dependency version examples in README.md to 2.8.0.