More language server feature work

[msullivan]

We have an LSP "language server now", but should support more features.

• non-DML commands (create role, create database, describe, ...)
• improve syntax errors (missing x errors are confusing in a lot of cases)
• run schema delta on .esdl files and report type+name errors,
• auto complete using the schema (select User.____, or select User { id, ____)
• type info on hover
• go to definition

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Code formatting could be part of this list, but it requires porting our AST to Rust, because we want a long-term solution.

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VSCode extension:

• provide a status bar with edgedb-ls version and current status of the server,
• a command to restart the server,
• a command to re-download latest version of the server,
• status bar: edgedb-ls not found,
• status bar: no dbschema/ dir,
• status bar: compiling schema,
• a setting for "path to the edgedb-ls binary", which would, when set, disable downloading from https://packages.edgedb.com,
• multi-root workspaces

[aljazerzen]

We also need to look into how much work would be support Windows. Maybe via WSL, same as our portable edgedb-server is started.