Add support of run time flags for enable Castanets

[v-saha]

This change adds runtime flag to enable castanets. Runtime flags --enable-forking, --server-address has been removed. Castanets can be verified as below,

Standalone mode: chrome

Castanets mode: Browser: chrome --enable-castanets Renderer: chrome --type=renderer --enable-castanets=<IP Address>

Signed-off-by: v-saha [email protected]