[Prism] Implement defined? for PM_MATCH_WRITE_NODE

Ruby code:

```ruby
defined?(/(?<foo>bar)/ =~ 'barbar')
```

Instructions:

```
"********* Ruby *************"
== disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(59,35)>
local table (size: 1, argc: 0 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] foo@0
0000 putobject                              "expression"              (  59)[Li]
0002 leave
"********* PRISM *************"
== disasm: #<ISeq:<compiled>@<compiled>:58 (58,0)-(58,35)>
local table (size: 1, argc: 0 [opts: 0, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] foo@0
0000 putobject                              "expression"              (  58)[Li]
0002 leave
```

Related: ruby/prism#2188

prism_compile.c

@@ -2554,6 +2554,7 @@ pm_compile_defined_expr0(rb_iseq_t *iseq, const pm_node_t *node, LINK_ANCHOR *co
       case PM_KEYWORD_HASH_NODE:
       case PM_LAMBDA_NODE:
       case PM_MATCH_PREDICATE_NODE:
+      case PM_MATCH_WRITE_NODE:
       case PM_NEXT_NODE:
       case PM_OR_NODE:
       case PM_RANGE_NODE:

test/ruby/test_compile_prism.rb

@@ -255,6 +255,7 @@ module Prism
       assert_prism_eval("defined?(def prism_test_def_node; end)")
       assert_prism_eval("defined?(for i in [1,2] do; i; end)")
       assert_prism_eval("defined?(if true; 1; end)")
+      assert_prism_eval("defined?(/(?<foo>bar)/ =~ 'barbar')")
     end
 
     def test_GlobalVariableReadNode