Add deprecation warning for constrain

[kevaundray]

Problem

As of #1227 we are deprecating constrain for assert. Since we don't want to break all existing Noir programs, we will for now just add a deprecation warning whenever constrain is used to tell folks to use assert.

Proposed solution

Add deprecation warning

Alternatives considered

No response

Additional context

No response

Submission Checklist

• Once I hit submit, I will assign this issue to the Project Board with the appropriate tags.

[joss-aztec]

I'm guessing the scope of this task includes removing all stdlib usages of constrain, since otherwise the user has to tolerate a ton of warnings.

[TomAFrench]

Linking #1251 to this issue as as Joss says, we need to address it first.

[joss-aztec]

Ah, we're in a bit of a tangle. They won't be able to fix the tests without fixing stldlib. Should I back my stdlib changes out, and leave that to the scope of #1275?

[joss-aztec]

Oh actually that's not true, because they won't encounter the depreciation warning because it's not merged yet 😅. It's just my PR that's blocked since the tests won't pass.