Add enum and comparison translators for cosmos

[ChrisJollyAU]

Adds the EnumMethod and Comparison translators to Cosmos.

• This supports the enum HasFlag and ToString
• Also adds .CompareTo (in comparison)

The above translators are almost the same as the relational version.

With the expressions, I needed to add in the CaseExpression which is straight from the relational version (easier if it ends up both having a common base in the future).

Query sql generator: Ouputs an IIF statement when processing a CaseExpression

Moved the respective tests to the new test classes.

Making this a draft as some of the enum ToString tests don't work yet. The below line (71) currently only returns null whereas in relational it is a unary convert node. I suspect if combined with #35000 that should be fine after that

_sqlExpressionFactory.Convert(instance, typeof(string))

Fixes #35317
Also continues #17246