feat: use macros to build completions statically

[lavafroth]

I wrote a macro to build both the HxCompletion slices and the map statically. The tradeoff: an HxCompletion has its members changed from String to &'static str.

[ThePrimeagen]

sorry that i haven't checked this out. my fault

[ThePrimeagen]

could you put a little blurp about why this is a good thing?

[lavafroth]

Without these static completions, the LSP would technically have to build the OnceCell singleton and populate it by generating the completion structs every time the LSP is run. With these changes, the stucts themselves are built and embedded into the binary. The binary wouldn't have to cobble them together every run. Also, no more pesky .get()s like the OnceCell because the static data can be guaranteed to exist.

[ThePrimeagen]

Would you like to resolve the conflicts and we can get this in?

[lavafroth]

There, we can merge this now.

[MNThomson]