Parameter schema

[bentsherman]

The language server should be able to use the nf-core parameter schema to determine the names and types of pipeline parameters. It should look for a schema file in the same directory as the main script.

More generally, any Nextflow script that defines an entry workflow should be able to define a parameter schema in the same directory.

Might want to wait until nextflow-io/nextflow#4669 is implemented

Actually might be helpful to do this in the language server first

[bentsherman]

Basic parameter validation is now supported

• Parameter validation is only performed in the entry workflow, as this is the only context in which the parameters are actually known
• The language server simply looks for ./nextflow_schema.json relative to the source file containing the entry workflow, so each "entry" script can define it's own parameter schema alongside it
• I don't inspect the schema file too deeply, I just grab the parameter names and types and go from there
• Both the old and new schema formats are implicitly supported by checking both defs and definitions
• Completion and hover hints are supported basically out of the box. Hover hint includes the parameter type and description
• Parameter type validation will be implemented as part of overall type checking