Extract Prisma support into an extension (#9820)

This PR extracts Prisma support into an extension and removes the
built-in Prisma support from Zed.

Release Notes:

- Removed built-in support for Prisma, in favor of making it available
as an extension. The Prisma extension will be suggested for download
when you open a `.prisma` file.

extensions/prisma/languages/prisma/config.toml

@@ -0,0 +1,9 @@
+name = "Prisma"
+grammar = "prisma"
+path_suffixes = ["prisma"]
+line_comments = ["// "]
+brackets = [
+    { start = "{", end = "}", close = true, newline = true },
+    { start = "[", end = "]", close = true, newline = true },
+    { start = "(", end = ")", close = true, newline = true }
+]

extensions/prisma/languages/prisma/highlights.scm

@@ -0,0 +1,26 @@
+[
+ "datasource"
+ "enum"
+ "generator"
+ "model"
+] @keyword
+
+(comment) @comment
+(developer_comment) @comment
+
+(arguments) @property
+(attribute) @function
+(call_expression) @function
+(column_type) @type
+(enumeral) @constant
+(identifier) @variable
+(string) @string
+
+"(" @punctuation.bracket
+")" @punctuation.bracket
+"[" @punctuation.bracket
+"]" @punctuation.bracket
+"{" @punctuation.bracket
+"}" @punctuation.bracket
+"=" @operator
+"@" @operator