Network bridge configuration option bridge.hwaddr should be configurable on a per-member basis

[kadinsayani]

Currently, the bridge.hwaddr (MAC address) configuration key for bridge networks may not be used as a member-specific key:

❯ lxc network create foo --type=bridge --target=devbox bridge.hwaddr=00:00:00:00:00:00
Error: Config key "bridge.hwaddr" may not be used as member-specific key

As mentioned by @simondeziel in this comment, this configuration option should have local scope rather than global scope, i.e. it should be able to be set on a per-member basis.