Enhance keep_tokens option for RubyVM::AbstractSyntaxTree parsing methods

Implementation for Language Server Protocol (LSP) sometimes needs token information.
For example both `m(1)` and `m(1, )` has same AST structure other than node locations
then it's impossible to check the existence of `,` from AST. However in later case,
it might be better to suggest variables list for the second argument.
Token information is important for such case.

This commit adds these methods.

* Add `keep_tokens` option for `RubyVM::AbstractSyntaxTree.parse`, `.parse_file` and `.of`
* Add `RubyVM::AbstractSyntaxTree::Node#tokens` which returns tokens for the node including tokens for descendants nodes.
* Add `RubyVM::AbstractSyntaxTree::Node#all_tokens` which returns all tokens for the input script regardless the receiver node.

[Feature #19070]

Impacts on memory usage and performance are below:

Memory usage:

```
$ cat test.rb
root = RubyVM::AbstractSyntaxTree.parse_file(File.expand_path('../test/ruby/test_keyword.rb', __FILE__), keep_tokens: true)

$ /usr/bin/time -f %Mkb /usr/local/bin/ruby -v
ruby 3.2.0dev (2022-11-19T09:41:54Z 19070-keep_tokens d3af1b8057) [x86_64-linux]
11408kb

# keep_tokens :false
$ /usr/bin/time -f %Mkb /usr/local/bin/ruby test.rb
17508kb

# keep_tokens :true
$ /usr/bin/time -f %Mkb /usr/local/bin/ruby test.rb
30960kb
```

Performance:

```
$ cat ../ast_keep_tokens.yml
prelude: |
  src = <<~SRC
    module M
      class C
        def m1(a, b)
          1 + a + b
        end
      end
    end
  SRC
benchmark:
  without_keep_tokens: |
    RubyVM::AbstractSyntaxTree.parse(src, keep_tokens: false)
  with_keep_tokens: |
    RubyVM::AbstractSyntaxTree.parse(src, keep_tokens: true)

$ make benchmark COMPARE_RUBY="./ruby" ARGS=../ast_keep_tokens.yml
/home/kaneko.y/.rbenv/shims/ruby --disable=gems -rrubygems -I../benchmark/lib ../benchmark/benchmark-driver/exe/benchmark-driver \
            --executables="compare-ruby::./ruby -I.ext/common --disable-gem" \
            --executables="built-ruby::./miniruby -I../lib -I. -I.ext/common  ../tool/runruby.rb --extout=.ext  -- --disable-gems --disable-gem" \
            --output=markdown --output-compare -v ../ast_keep_tokens.yml
compare-ruby: ruby 3.2.0dev (2022-11-19T09:41:54Z 19070-keep_tokens d3af1b8057) [x86_64-linux]
built-ruby: ruby 3.2.0dev (2022-11-19T09:41:54Z 19070-keep_tokens d3af1b8057) [x86_64-linux]
warming up..

|                     |compare-ruby|built-ruby|
|:--------------------|-----------:|---------:|
|without_keep_tokens  |     21.659k|   21.303k|
|                     |       1.02x|         -|
|with_keep_tokens     |      6.220k|    5.691k|
|                     |       1.09x|         -|
```

1 files changed, 32 insertions, 4 deletions

diff --git a/test/ruby/test_ast.rb b/test/ruby/test_ast.rb
index acf6722bb7..c3de36b4fb 100644
--- a/test/ruby/test_ast.rb
+++ b/test/ruby/test_ast.rb
@@ -132,6 +132,34 @@ class TestAst < Test::Unit::TestCase
     end
   end
 
+  Dir.glob("test/**/*.rb", base: SRCDIR).each do |path|
+    define_method("test_all_tokens:#{path}") do
+      node = RubyVM::AbstractSyntaxTree.parse_file("#{SRCDIR}/#{path}", keep_tokens: true)
+      tokens = node.all_tokens.sort_by { [_1.last[0], _1.last[1]] }
+      tokens_bytes = tokens.map { _1[2]}.join.bytes
+      source_bytes = File.read("#{SRCDIR}/#{path}").bytes
+
+      assert_equal(source_bytes, tokens_bytes)
+
+      (tokens.count - 1).times do |i|
+        token_0 = tokens[i]
+        token_1 = tokens[i + 1]
+        end_pos = token_0.last[2..3]
+        beg_pos = token_1.last[0..1]
+
+        if end_pos[0] == beg_pos[0]
+          # When both tokens are same line, column should be consecutives
+          assert_equal(beg_pos[1], end_pos[1], "#{token_0}. #{token_1}")
+        else
+          # Line should be next
+          assert_equal(beg_pos[0], end_pos[0] + 1, "#{token_0}. #{token_1}")
+          # It should be on the beginning of the line
+          assert_equal(0, beg_pos[1], "#{token_0}. #{token_1}")
+        end
+      end
+    end
+  end
+
   private def parse(src)
     EnvUtil.suppress_warning {
       RubyVM::AbstractSyntaxTree.parse(src)
@@ -705,11 +733,11 @@ dummy
         a = 1
       else
     STR
-      (SCOPE@1:0-3:5
+      (SCOPE@1:0-3:4
        tbl: [:a]
        args: nil
        body:
-         (IF@1:0-3:5 (VCALL@1:3-1:7 :cond) (LASGN@2:2-2:7 :a (LIT@2:6-2:7 1))
+         (IF@1:0-3:4 (VCALL@1:3-1:7 :cond) (LASGN@2:2-2:7 :a (LIT@2:6-2:7 1))
             (BEGIN@3:4-3:4 nil)))
     EXP
   end
@@ -732,11 +760,11 @@ dummy
         a = 1
       else
     STR
-      (SCOPE@1:0-3:5
+      (SCOPE@1:0-3:4
        tbl: [:a]
        args: nil
        body:
-         (UNLESS@1:0-3:5 (VCALL@1:7-1:11 :cond) (LASGN@2:2-2:7 :a (LIT@2:6-2:7 1))
+         (UNLESS@1:0-3:4 (VCALL@1:7-1:11 :cond) (LASGN@2:2-2:7 :a (LIT@2:6-2:7 1))
             (BEGIN@3:4-3:4 nil)))
     EXP
   end