Deprecate `get_action_traces`

[abourget]

dfuse Search is MUCH more reliable (see the cursor-based streaming protocol), much more performant, thinner on the bandwidth, and more flexible in terms of queries.

There are no reasons it should stick around, other than people still using it. Let's start by deprecating it.

One thing that is left as a "feature" in there, is that it will match Expired/Failed deferred transactions. Two things about this:

1. maybe some users would actually be surprised that this stream involves failed trx, they don't check the status and we should remove them ASAP!
2. maybe someone desperately needs those expired/failed because there's no other way to catch it: for that case, we could tweak search to optionally index those failures, according to their specific needs.

In any case, we'll want a comms plan to go about that deprecation.