Adds conformance DSL syntax check

[popematt]

Issue #, if available:

None

Description of changes:

Adds a CI check for the conformance test DSL.

Still TODO—decide whether we want to use binary or bytes. My preference is binary since it refers to the binary encoding, the conformance DSL grammar in the README file uses binary, but I think most or all of the tests use bytes.

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[jobarr-amzn]

Is it possible to simplify the ISL somehow?

[popematt]

Is it possible to simplify the ISL somehow?

Simplify in what sort of way? There are trade offs. Fewer type definitions? DRY it up more? Flatten nested types?

[toddjonker]

I think the byte-input form should be able to represent text as well as binary Ion data, so we can verify UTF-8 handling, BOM, etc. In other words, I think the term should be the more general bytes

[popematt]

I think the byte-input form should be able to represent text as well as binary Ion data, so we can verify UTF-8 handling, BOM, etc. In other words, I think the term should be the more general bytes

I realize that maybe I was not clear in my initial comments. I was referring to the keyword for the Ion binary fragment form. One of the motivations for adding this ISL grammar is because we've had inconsistent use of (binary ... and (bytes ... for Ion binary fragments. (This ISL grammar was implemented to allow both because of that, but we need to make a decision and clean it up one way or the other.)

Are you saying that the Ion binary fragment form should in fact be a more general "bytes" that is usable for text data?