Simplify AuthenticationMethod type and PIN hash handling.
1 Previously AuthenticationMethod was a class. Replaced
it with a simple enum.
2 Removed SharedSecretHash struct and simplified the code
that passes around PIN hash.
3 If the host config contains PIN in plain text then now
the host hashes it instead of using spake2_plain
authenticator method. This means that spake2_hmac is
always used for Me2Me even when the PIN is not hashed
in the config.
This change will make it easier to add new authentication
methods.
BUG=589698
Review URL: https://codereview.chromium.org/1755273003
Cr-Commit-Position: refs/heads/master@{#379365}
22 files changed
