Convert LSP URIs into custom URIs

This introduces a custom URI type in core meant to be extended later
if we want to support other schemes. For now it's just a wrapper over a
PathBuf. We use this new URI type to firewall `lsp::Url`. This was
previously done in 8141a4a but using a custom URI type is more flexible
and will improve the way Pickers handle paths for previews in the child
commit(s).

Co-authored-by: soqb <cb.setho@gmail.com>

helix-core/Cargo.toml

@@ -34,6 +34,7 @@ bitflags = "2.6"
 ahash = "0.8.11"
 hashbrown = { version = "0.14.5", features = ["raw"] }
 dunce = "1.0"
+url = "2.5.0"
 
 log = "0.4"
 serde = { version = "1.0", features = ["derive"] }