Pass IV through cipher resets for OpenSSL and Android

[vcsjones]

The Reset method accepted an IV, but for OpenSSL and Android, the IV was discarded. Instead, the IV that was originally used to create the cipher context was used.

This wasn't a problem because we've always considered the Key and IV a tuple that belong together. The Lite ciphers are meant to decouple the key from the IV, so the cipher instance can be re-used with different IVs.

In order to facilitate re-usable lite cipher instances with different IVs, all platforms need to support resetting with a different IV than when it was originally constructed.

This also simplifies the reset on OpenSSL since the managed side always supplies the IV, and removes a workaround from OpenSSL 3.

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Issue Details

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The Reset method accepted an IV, but for OpenSSL and Android, the IV was discarded. Instead, the IV that was originally used to create the cipher context was used.

This wasn't a problem because we've always considered the Key and IV a tuple that belong together. The Lite ciphers are meant to decouple the key from the IV, so the cipher instance can be re-used with different IVs.

In order to facilitate re-usable lite cipher instances with different IVs, all platforms need to support resetting with a different IV than when it was originally constructed.

This also simplifies the reset on OpenSSL since the managed side always supplies the IV, and removes a workaround from OpenSSL 3.

Author:	vcsjones
Assignees:	vcsjones
Labels:	area-System.Security
Milestone:	-

[vcsjones]

I ran the Android tests locally and everything passed, I'm uncertain if CI is covering Android right now, but I suspect not.

[vcsjones]

/azp run runtime

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[vcsjones]

Guessing it didn't run because I merged / pushed when GitHub was unavailable yesterday.

[bartonjs]

runtime (Libraries Test Run checked coreclr OSX x64 Debug) failure is that the test matrix still contain{s/ed} an entry for macOS 10.14, but we've shut down that machine configuration.

Since everything else passed, and this change doesn't affect OSX anyways, merging.