This is a rather large refactor that moves most of the code for
loading, fetching, and building grammars into a new helix-loader
module. This works well with the [[grammars]] syntax for
languages.toml defined earlier: we only have to depend on the types
for GrammarConfiguration in helix-loader and can leave all the
[[language]] entries for helix-core.
* Move runtime file location definitions to core
* Add basic --health command
* Add language specific --health
* Show summary for all langs with bare --health
* Use TsFeature from xtask for --health
* cargo fmt
Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>