feat: [sc-58279] [core] add tiledb_array_schema_get_enumeration API

[rroelke]

Story details: https://app.shortcut.com/tiledb-inc/story/58279

In tiledb-rs we have have "property-based testing" strategies which generate arbitrary tiledb schema. We would like to extend these strategies to generate arbitrary enumerations to put in those schemata.

As a step towards this we must add an API tiledb_array_schema_get_enumeration so that we can load the values in an enumeration without having a pointer to the open array in the same function.

It is not required for this API to actually load the enumeration, just to return its contents if it is already loaded. There should be a graceful signal to distinguish between an enumeration not being found and an enumeration not being loaded.

This pull request implements the above and adds unit tests which demonstrate that tiledb_array_schema_get_enumeration abides by the above:

1. if there is no enumeration with the requested name attached to the schema, we throw an exception.
2. if there is an enumeration with the requested name attached to the schema but it has not been loaded, we return NULL.
3. if there is an enumeration with the requested name attached to the schema and it has been loaded in some way, we return the enumeration.

This pull request does not attempt to bridge the gap between 2 and 3, i.e. load the enumeration when it is requested.

---

TYPE: FEATURE | C_API | CPP_API
DESC: add tiledb_array_schema_get_enumeration

[shaunrd0]

Just left some small comments, looks great so far 👍

[davisp]

+1 from me. @ypatia already suggested the REST test which is all I had thought of.

[rroelke]

+1 from me. @ypatia already suggested the REST test which is all I had thought of.

@davisp I mis-clicked when I requested a re-review, but feel free :)

All the changes are strictly in response to the review comments.

[shaunrd0]

Nice! 👍