utils: Implement hooks in ipc-tap and ipc-inject

utils: Implement hooks in ipc-tap and ipc-inject

To correctly forward foundry messages using ipc-tap and ipc-inject,
it is necessary to move data that is usually not transferred over
IPC messages. In order to transfer this data over ipc-tap and
ipc-inject, hooks are necessary that allow user-data to be generated
on the ipc-tap side and consumed on the ipc-inject side.

This commit implements a simple mechanism that allows the user to
specify hooks that are called by ipc-tap whenever a message on a
user-defined topic is encountered. The hook can then inject
messages into ipc-tap's data stream. On the ipc-inject side, the
user may define hooks that are called when a user-message with a
application-defined tag is encountered, allowing the injected
message to be handled on the ipc-inject side.