Improve performance of reading escaped string (#948)

This patch will improve the performance of reading escaped string
by using a lookup table.

−       | before  | after   | result
--      | --      | --      | --
Oj.load | 601.508 | 654.004 | 1.087x

### Environment
- Linux
  - Manjaro Linux x86_64
  - Kernel: 6.12.4-1-MANJARO
  - AMD Ryzen 9 8945HS
  - gcc version 14.2.1
  - Ruby 3.4.1

### Code
```ruby
require 'bundler/inline'
gemfile do
  source 'https://rubygems.org'
  gem 'benchmark-ips'
  gem 'oj'
end

# https://github.com/miloyip/nativejson-benchmark/blob/master/data/twitter.json
json = File.read('twitter.json')

Benchmark.ips do |x|
  x.time = 10
  x.report('Oj.load compat') { Oj.load(json, mode: :compat) }
end
```

### Before
```
$ ruby json_load.rb
ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
Warming up --------------------------------------
      Oj.load compat    59.000 i/100ms
Calculating -------------------------------------
      Oj.load compat    601.508 (± 1.2%) i/s    (1.66 ms/i) -      6.018k in  10.006395s
```

### After
```
$ ruby json_load.rb
ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
Warming up --------------------------------------
      Oj.load compat    64.000 i/100ms
Calculating -------------------------------------
      Oj.load compat    654.004 (± 1.7%) i/s    (1.53 ms/i) -      6.592k in  10.082170s
```

ext/oj/parse.c

@@ -183,9 +183,19 @@ static void unicode_to_chars(ParseInfo pi, Buf buf, uint32_t code) {
     }
 }
 
+static const unsigned char end_of_scan_string[] = {
+    // Filled 1 at the positions of '\0', '\\', and '"'
+    1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+};
 static inline const char *scan_string_noSIMD(const char *str, const char *end) {
-    for (; '"' != *str; str++) {
-        if (end <= str || '\0' == *str || '\\' == *str) {
+    for (; str < end; str++) {
+        if (end_of_scan_string[(unsigned char)*str]) {
             break;
         }
     }