support drivers that can't use reset directly.

[barbibulle]

This should allow a driver to interact with a controller, via the host, before any command, including RESET is issued.
See the example with the Realtek driver.
Note that if a driver needs to send a command and receive a response before RESET is performed, it must set host.ready = True to allow the inbound packet processing to accept the packet even if no RESET has been done (by default, the host ignores packets from the controller that are received before a RESET).

Also included is a generic way to add HCI metadata to an HCI transport source. Previously, only certain transport sources would set metdata (USB would set vendor_id and product_id, which the Realtek driver uses to determine if it should try
to load a FW image). Now, a driver can be "forced" for a specific HCI source, when no relevant metadata is available (for
example, when the controller is only visible via a transport that does not set metadata, like a serial port or TCP socket).
Any number of metadata key=value pairs can be added to a transport name, in square brackets, after the transport type.
Example: usb:[driver=rtk]0 would "inject" a "driver" metadata entry for the usb transport, which the Realtek driver will see as a request that this driver be activated, even if the vendor_id and product_id are not present, or don't match the internal allow-list.