Change constrain key word to assert

[kevaundray]

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[kevaundray]

If we are going to do this change, it should be sooner rather than later.

My suggestion is to allow constrain and assert for about a year, but change all documentation to use assert.

This way existing programs are not broken and newer programs are discouraged from using it. A lint would also be good here, to notify existing programs that it is being phased out.

Cc @jfecher @guipublic @vezenovm

[jfecher]

I am fine with constrain or assert. The later would be more familiar to those coming from other languages, but perhaps constrain is clearer for those already in the ZKPL space?

The change is fairly trivial to make if we do want to change to assert. I'll also suggest we can issue a deprecation warning for constrain while in this intermediate period of allowing both.

[kevaundray]

pinging @sirasistant for visibility