[fidl] Fix the last usages of raw channels
A previous change migrated most use of LLCPP to typed channels but
missed a few. They were caught when we started conditionally deprecating
parts of the raw channel API in
http://fxrev.dev/I74a349e08190df75abd21b3fb6286d84687dc553
This change fixes them until the code builds successfully. Unfortunately
the code gets slightly more verbose as a result, because many operations
interface with raw zx_handle_t during service discovery. Moving the
GetConnectToServiceFunction to look more similar to
`service::Connect<Protocol>` could simplify some of those in the future.
TEST: Fuchsia GI.
Change-Id: I3edbc488f0458a4cc461f588e708f1edc2d750b7
5 files changed
