Rewrite hover provider in Rego (#1951)

And get rid of all related code previously written in Go. The biggest
win here is IMO how this allows us to entirely get rid of one of our
continuous "watcher" processes, and instead use only data from input
and storage, like we do in all Rego handlers. Quite an improvement!

Notable other changes:
- Move ast.keywords to lsp.hover.keywords as they're only used in hover
- Move lsp.completion.location to lsp.location as useful outside completion handlers

Besides the tests, also manually tested hovering both built-ins and keywords
and all seem to work well!

Fixes #1905

Signed-off-by: Anders Eknert <anders.eknert@apple.com>

Author: anderseknert

.github/workflows/update-example-index.yaml

@@ -3,7 +3,7 @@
 package regal.lsp.completion.providers.booleans
 
 import data.regal.lsp.completion.kind
-import data.regal.lsp.completion.location
+import data.regal.lsp.location
 
 # METADATA
 # description: completion suggestions for true/false

build/workflows/update_example_index.rego

@@ -3,7 +3,7 @@
 package regal.lsp.completion.providers.builtins
 
 import data.regal.lsp.completion.kind
-import data.regal.lsp.completion.location
+import data.regal.lsp.location
 
 # METADATA
 # description: suggest built-in functions matching typed ref

bundle/regal/ast/keywords_test.rego

@@ -4,7 +4,7 @@
 package regal.lsp.completion.providers.commonrule
 
 import data.regal.lsp.completion.kind
-import data.regal.lsp.completion.location
+import data.regal.lsp.location
 
 _suggested_names := {
 	"allow",

bundle/regal/lsp/completion/providers/booleans/booleans.rego

@@ -5,7 +5,7 @@ package regal.lsp.completion.providers.default
 import data.regal.ast
 
 import data.regal.lsp.completion.kind
-import data.regal.lsp.completion.location
+import data.regal.lsp.location
 
 # METADATA
 # description: all completion suggestions for default keyword