feat: enable raw pointer return from scripts

[iqdecay]

• This PR enables returning heap types from scripts.
• In feat: support returning Vec<> types from contracts fuels-rs#848, support was added for
  returning vectors from smart contracts in the SDK, this safeguard can now be
  removed so the same can happen with scripts.

[otrho]

Hrmm, I'm not sure this is necessarily what we want. Returning a Vec can be special-cased, and should be returned using a RETD of the vector contents, I assume? Is that right?

But just returning a raw_ptr using RET doesn't make sense and was banned for a reason. A better solution might be to convert the Vec to a raw_slice which we already allow, and to return that..?

[iqdecay]

I'm just trying to support returning Vec and Bytes types from a script, which is not currently supported because of the safeguard that I remove in this PR. @mohammadfawaz had told me that this safeguard was here just because the SDK didn't support it, so I naively assumed that just removing the safeguard was enough.

[iqdecay]

Closing in favor of an upcoming PR.

[iqdecay]

Reopening the PR after a discussion with Toby. Currently, contracts can return raw_ptr, and for coherence there is no reason to prevent scripts from doing so too, this way the SDK can handle scripts returning vectors.