Enable concurrent feature for miden-tx in bench-transaction

[Al-Kindi-0]

While working on a variation of #2391, found the issue probably causing 0xMiden/node#1862

[bobbinth]

cc @Mirko-von-Leipzig and @igamigo in case this is relevant in node/client.

[igamigo]

In the client we do enable concurrent everywhere we can, but it seems that we don't in the node. Created a PR here. I think running integration tests from the client does get a little faster, but not by a lot (and still if I run on the previous level of concurrency the contention still kills the machine).

[bobbinth]

In the client we do enable concurrent everywhere we can, but it seems that we don't in the node. Created a PR here.

Approved! I do wonder if we should just always enable concurrent when std is enabled. I don't see a reason why we'd want to run with std but not concurrent.

[Mirko-von-Leipzig]

In the client we do enable concurrent everywhere we can, but it seems that we don't in the node. Created a PR here.

Approved! I do wonder if we should just always enable concurrent when std is enabled. I don't see a reason why we'd want to run with std but not concurrent.

If you do then please just remove the feature entirely? Having features that should always be selected is.. just weird