Autocompletion for CodeSystems

[JPercival]

As a CQL author, I want the editor to suggest some CodeSystems when making references to them.

Within a IG that contains CodeSystems it ought to suggest whatever code systems are available locally. If not, it ought to suggest well-known CodeSystems such as LOINC, SnoMed, RxNorm, etc.

[JPercival]

https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_completion