[ruby/yarp] fix: regular expression with start and end out of order

Also, a similar test and fix for interpolated regular expressions.

This snippet:

    <<-A.g//,
    A
    /{/, ''\

previously created a regular expression node with inverted start and
end:

    RegularExpressionNode(14...13)((14...15), (15...21), (12...13), ", ''", 0),

which failed an assertion during serialization.

After this change:

    RegularExpressionNode(12...15)((14...15), (15...21), (12...13), ", ''", 0),

Found by the fuzzer.

https://github.com/ruby/yarp/commit/5fef572f95

test/yarp/fuzzer_test.rb

@@ -33,5 +33,16 @@ module YARP
       A
       /, ""\\
     EOF
+    snippet "regular expression with start and end out of order", <<~RUBY
+      <<-A.g//,
+      A
+      /{/, ''\\
+    RUBY
+    snippet "interpolated regular expression with start and end out of order", <<~RUBY
+      <<-A.g/{/,
+      A
+      a
+      /{/, ''\\
+    RUBY
   end
 end

yarp/yarp.c

@@ -2766,8 +2766,13 @@ yp_interpolated_regular_expression_node_create(yp_parser_t *parser, const yp_tok
 
 static inline void
 yp_interpolated_regular_expression_node_append(yp_interpolated_regular_expression_node_t *node, yp_node_t *part) {
+    if (node->base.location.start > part->location.start) {
+        node->base.location.start = part->location.start;
+    }
+    if (node->base.location.end < part->location.end) {
+        node->base.location.end = part->location.end;
+    }
     yp_node_list_append(&node->parts, part);
-    node->base.location.end = part->location.end;
 }
 
 static inline void
@@ -3600,8 +3605,8 @@ yp_regular_expression_node_create(yp_parser_t *parser, const yp_token_t *opening
             .type = YP_NODE_REGULAR_EXPRESSION_NODE,
             .flags = yp_regular_expression_flags_create(closing),
             .location = {
-                .start = opening->start,
-                .end = closing->end
+                .start = MIN(opening->start, closing->start),
+                .end = MAX(opening->end, closing->end)
             }
         },
         .opening_loc = YP_LOCATION_TOKEN_VALUE(opening),