nft-bridge: pass context structure to ops->add() to improve anonymous set support

nft-bridge: pass context structure to ops->add() to improve anonymous set support

Add context structure to improve bridge among support which creates an
anonymous set. This context structure specifies the command and it
allows to optionally store a anonymous set.

Use this context to generate native bytecode only if this is an
add/insert/replace command.

This fixes a dangling anonymous set that is created on rule removal.

Fixes: 26753888720d ("nft: bridge: Rudimental among extension support")
Reported-and-tested-by: Igor Raits <igor@gooddata.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>