src: meta: always prefix 'meta' for almost all tokens

src: meta: always prefix 'meta' for almost all tokens

got following bug report:

nft add ... ct mark set mark and 0x10

... always sets 0.
What reporter meant to write instead was 'ct mark', not 'mark'.

We can't just remove support for 'mark' and force
'meta mark', but we can start to discourage it by printing meta prefix too.

Later on, we could start to print deprecation warning if needed.
Followup patch can also change
"iifname" etc. to "meta iifname".

Signed-off-by: Florian Westphal <fw@strlen.de>