Generate a qemu_plugin_api.lib delay import lib on windows, for
windows qemu plugins to link against.

Implement an example dll load fail hook to link up the API functions
correctly when a plugin is loaded on windows.

Update the build scripts for the test and example plugins to use these
things.

Signed-off-by: Greg Manning <gmanning@rapitasystems.com>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231102172053.17692-3-gmanning@rapitasystems.com>
[AJB: use find_program for dlltool, s/Windows/windows/]
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231106185112.2755262-15-alex.bennee@linaro.org>