TIAF: add signing request and result

Detailed call sequence can be found at
go/tiaf-use-cases

And add INTENT_KEY_COMMAND_TYPE

Bug: 224121339
Bug: 225082750
Test: atest testRequestSigning
Test: atest testSendSigningResult

Change-Id: I32b7e77dc7fc357ce168f486c28c16863bbbb3bf
9 files changed