[Feat] Consensus-restricted keywords.

[d0cd]

Motivation

As programming standards evolve on Aleo, it would be useful to be able to enforce syntactic restrictions at the consensus layer. This PR:

• adds a mechanism for describing versioned syntax restrictions and enforces them in check_transactions.
• adds a CI runner with the test feature enabled for the synthesizer crate.

Test Plan

A test was added verifying that syntax restrictions are not enforced before a given version height and that they are enforced after.

[d0cd]

@reviewers I'm not too happy with the name RESTRICTED_KEYWORDS, any ideas for a better one?

[acoglio]

RESERVED_KEYWORDS is perhaps more common?

[vicsn]

LGTM! Left two style suggestions.

synthesizer CI is failing when run with the --test feature because test_migration_v3_maximum_validator_increase assumes max validator set increases at consensus v3, whereas with the test feature enabled the max validator set is static at 100.

In other words, our usage of the test feature is a bit of an undocumented mess.

As a "quickfix", one option would be to use the same sample_finalize_state approach as in test_migration_v3_maximum_validator_increase, and then we can also get rid of introducing yet another CI job.

[d0cd]

RESERVED_KEYWORDS is perhaps more common?

I had mapped the concept of "reserved" keywords to the KEYWORDS array.
This feels more like syntactic recommendations to me.
Like linting...?

[d0cd]

As a "quickfix", one option would be to use the same sample_finalize_state approach as in test_migration_v3_maximum_validator_increase, and then we can also get rid of introducing yet another CI job.

If it's not too costly, it might be nice to have a CI run with the test feature enabled.
I noticed a few other tests (1, 2, 3, 4, 5) that also use it.

[niklaslong]

LGTM overall, pending the changes requested by other reviewers.