GH-905 Implement authorized_keys from and expiry-time checks

[Unbbal]

This PR implements the missing authorized_keys option checks tracked in GH-905.

Changes:

• Enforce the expiry-time option before accepting a matching authorized_keys entry.
• Enforce the from option using the client address, with support for address/hostname patterns, negation, and CIDR ranges.
• Prefer ServerSession#getClientAddress(), falling back to getRemoteAddress().
• Reject invalid from patterns and invalid expiry-time values fail-closed.
• Add unit tests for matching from, rejected from, CIDR, negation, invalid from, future expiry-time, and expired keys.

Tests:

• .\mvnw.cmd -pl sshd-core -am -Dtest=AuthorizedKeyEntriesPublickeyAuthenticatorTest '-Dsurefire.failIfNoSpecifiedTests=false' test

[tomaswolf]

Thanks a lot for this contribution! Looks good; the test could be simplified.

[tomaswolf]

Use Mockito for this. Simply

    private static ServerSession session(InetSocketAddress remote) {
        ServerSession session = Mockito.mock(ServerSession.class);
        Mockito.when(session.getClientAddress()).thenReturn(remote);
        Mockito.when(session.getRemoteAddress()).thenReturn(remote);
        return session;
    }