[fastx adapter] Cache the VM to amortise module verification

[gdanezis]

@oxade this uses your PR #190 as a base, so we can merge or we can look at it separately.

[gdanezis]

Yo @sblackshear and @lxfind -- I am now starting to encroach on the adaptor to get more familiar with it, and be able to help on this side. Do check I am not doing anything too daft, and let me know how you prefer to structure passing in a pre-existing MoveVM to execute.

[oxade]

@oxade this uses your PR #190 as a base, so we can merge or we can look at it separately.

Please give me s short moment to address the comments on the PR w.r.t using Coin::transfer, then we can integrate :)

[gdanezis]

There is no rush to take this. It's just a demo of the kind of change we would need to do to reuse the VM. As you can see it's a small change but I would rather others chip in on how best to do this.

[sblackshear]

Good catch + this looks very sensible to me!

One thing that comes to mind is the (lack of) eviction policy for the VM's caches. Not a blocker for this, but could bite us going forward, so I filed diem/move#18 to get the Move team thinking about it.

[sblackshear]

LGTM modulo deleting the native_functions field.

[sblackshear]

We can get rid of this field now, since we only use it to create a VM inside the adapter.

[gdanezis]

Thanks @sblackshear ; @oxade the comments have been addressed so feel free to land this onto your branch whenever you like.

[oxade]

Thanks @sblackshear ; @oxade the comments have been addressed so feel free to land this onto your branch whenever you like.

Cherrypicked the changes. Thank you

[oxade]

Closing this since #190 is merged