VmBus: allow for port/connection-based SynicPortAccess #1519

Job	Run time
build artifacts [x64-linux]	6m 11s
build openhcl [aarch64-linux]	5m 33s
build mdbook guide	2m 30s
build and check docs [x64-windows]	10m 36s
build openhcl [x64-linux]	7m 59s
clippy [windows], unit tests [x64-windows]	12m 11s
clippy [linux, macos], unit tests [x64-linux]	8m 14s
clippy [linux-musl, misc nostd], unit tests [x64-linux-musl]	7m 21s
unit tests [aarch64-windows]	7m 8s
build and check docs [x64-linux]	2m 53s
test flowey local backend	3m 19s
xtask fmt (linux)	2m 24s
build artifacts (not for VMM tests) [aarch64-windows]	5m 54s
build artifacts (for VMM tests) [aarch64-windows]	8m 44s
build artifacts (not for VMM tests) [x64-windows]	6m 0s
build artifacts (for VMM tests) [x64-windows]	8m 44s
build artifacts [aarch64-linux]	5m 34s
xtask fmt (windows)	7m 23s
run vmm-tests [x64-windows-amd]	11m 29s
run vmm-tests [x64-windows-intel]	9m 26s
run vmm-tests [x64-linux]	3m 33s
run vmm-tests [aarch64-windows]	6m 33s
openvmm checkin gates	7s
	2h 29m 46s

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