Remove SqlLiteral re-wrapping from Arel.sql

Previously, passing a SqlLiteral to Arel.sql would wrap the SqlLiteral
in a new SqlLiteral (which is generally unnecessary since it allocates a
new SqlLiteral/String).

This commit updates Arel.sql to no longer perform the wrapping of the
given "sql_string" is already a SqlLiteral.

Author: skipkayhil

activerecord/lib/active_record/relation/query_methods.rb

@@ -1624,11 +1624,7 @@ def build_where_clause(opts, rest = []) # :nodoc:
         case opts
         when String
           if rest.empty?
-            if Arel.arel_node?(opts)
-              parts = [opts]
-            else
-              parts = [Arel.sql(opts)]
-            end
+            parts = [Arel.sql(opts)]
           elsif rest.first.is_a?(Hash) && /:\w+/.match?(opts)
             parts = [build_named_bound_sql_literal(opts, rest.first)]
           elsif opts.include?("?")

activerecord/lib/arel.rb

@@ -50,7 +50,9 @@ module Arel
   # Use this option only if the SQL is idempotent, as it could be executed
   # more than once.
   def self.sql(sql_string, *positional_binds, retryable: false, **named_binds)
-    if positional_binds.empty? && named_binds.empty?
+    if Arel::Nodes::SqlLiteral === sql_string
+      sql_string
+    elsif positional_binds.empty? && named_binds.empty?
       Arel::Nodes::SqlLiteral.new(sql_string, retryable: retryable)
     else
       Arel::Nodes::BoundSqlLiteral.new sql_string, positional_binds, named_binds