Increase performance in Liquid::Lexer#tokenize
Increase performance in Liquid::Lexer#tokenize

To obtain String Literal, the regular expression might be executed at two times.
It would be slightly faster to run them all at once using `Regexp.union`.

−               | before   | after   | result
--               | --       | --      | --
parse            | 63.418   | 65.183  | 1.028x
render           | 195.389  | 195.648 | -
parse & render   | 46.091   | 46.917  | 1.018x

### Environment
- MacBook Pro (14 inch, 2021)
- macOS 13.0 Beta
- Apple M1 Max
- Ruby 3.1.2

### Before
```
Running benchmark for 10 seconds (with 5 seconds warmup).

Warming up --------------------------------------
              parse:     6.000  i/100ms
             render:    19.000  i/100ms
     parse & render:     4.000  i/100ms
Calculating -------------------------------------
              parse:     63.418  (± 0.0%) i/s -    636.000  in  10.028939s
             render:    195.389  (± 0.5%) i/s -      1.957k in  10.016466s
     parse & render:     46.091  (± 0.0%) i/s -    464.000  in  10.067445s
```

### After
```
Running benchmark for 10 seconds (with 5 seconds warmup).

Warming up --------------------------------------
              parse:     6.000  i/100ms
             render:    19.000  i/100ms
     parse & render:     4.000  i/100ms
Calculating -------------------------------------
              parse:     65.183  (± 0.0%) i/s -    654.000  in  10.033549s
             render:    195.648  (± 1.0%) i/s -      1.957k in  10.003511s
     parse & render:     46.917  (± 0.0%) i/s -    472.000  in  10.060782s
```

Shopify/liquid