Use @boolean for true and false in highlights (#25338)

Release Notes:

- Fixed issue where `true` and `false` were highlighted as constants,
ignoring the `boolean` highlight defined in themes.
  - This fix applies to: C, C++, Go, JSON, JSONC, Python, and Rust.

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/languages/src/c/highlights.scm

@@ -102,8 +102,9 @@
 [
   (true)
   (false)
-  (null)
-] @constant
+] @boolean
+
+(null) @constant
 
 (identifier) @variable
 

crates/languages/src/cpp/highlights.scm

@@ -153,6 +153,9 @@ type :(primitive_type) @type.primitive
 [
   (true)
   (false)
+] @boolean
+
+[
   (null)
   ("nullptr")
 ] @constant

crates/languages/src/go/highlights.scm

@@ -118,6 +118,9 @@
 [
   (true)
   (false)
+] @boolean
+
+[
   (nil)
   (iota)
 ] @constant.builtin

crates/languages/src/json/highlights.scm

@@ -11,6 +11,9 @@
 [
   (true)
   (false)
+] @boolean
+
+[
   (null)
 ] @constant
 

crates/languages/src/jsonc/highlights.scm

@@ -11,6 +11,9 @@
 [
   (true)
   (false)
+] @boolean
+
+[
   (null)
 ] @constant
 

crates/languages/src/python/highlights.scm

@@ -95,9 +95,12 @@
 ; Literals
 
 [
-  (none)
   (true)
   (false)
+] @boolean
+
+[
+  (none)
   (ellipsis)
 ] @constant.builtin
 

crates/languages/src/rust/highlights.scm

@@ -129,7 +129,7 @@
   (float_literal)
 ] @number
 
-(boolean_literal) @constant
+(boolean_literal) @boolean
 
 [
   (line_comment)