VS Code extensions providing code snippets APIs make not usable in CRW

A popular kind of extensions for VS Code provide code snippets, which provide valuable productivity tools for developers or often collections of standard code patterns that developer would have otherwise have to copy from reference manuals. The are particularly popular for Enterprise Application developers. IBM's Z Open Editor ships with 200 snippets and IBM's DB2 for z/OS extension also comprises of a larger collection of standards patterns for writing DDLs and stored procedures.

The following issues filed against Che and Theia break the usage of code snippets almost entirely.  VS Code extension developers would not be able to provide their snippets as a json file that is loaded at runtime, but have to encode their snippets into VS Code Completion Item providers, which significantly raised the effort developers need to undergo just for Che support.

https://github.com/eclipse/che/issues/16502

https://github.com/eclipse/che-theia/pull/948