Eliminate PasswordAutofillAgentConstructed() in mojo interface PasswordManagerDriver
PasswordAutofillAgentConstructed() is just for autofill::PasswordAutofillAgent to
get logging state from browser side when PasswordAutofillAgent is created.
It's useful before due to lack of pending mechanism for legacy IPCs,
but now in mojo world we can achieve this goal without it.
This CL lets browser side just send logging state as soon as it's ready,
even at that timing point renderer process has not started or has not created
PasswordAutofillAgent, the mojo call
autofill::mojom::PasswordAutofillAgent::SetLoggingState() will be cached
inside mojo message pipe and be executed immediately once PasswordAutofillAgent
instantiates and binds itself with the pending mojo connection.
This keeps exactly the same behavior with before:
autofill::mojom::PasswordAutofillAgent::SetLoggingState() is always the first
mojo call arriving at autofill::PasswordAutofillAgent from browser side.