feat(schema): Add allequal(x: array, y: array) to expression language

[effigies]

It turns out, in javascript, [1] != [1] because equality is object equality. We can either parse the expression language and build an AST or we can add an allequal() function and move on with our lives.

@rwblair This is mostly a notice. Feel free to approve, but I'm going to merge in the absence of objections.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.04%. Comparing base (40af25c) to head (0970e1c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1837 +/- ## ======================================= Coverage 88.04% 88.04% ======================================= Files 16 16 Lines 1380 1380 ======================================= Hits 1215 1215 Misses 165 165 ```

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