Faster Variable BlockBody Matching

[ggmichaelgo]

Benchmark testing result:

bundle exec rake benchmark:run 

Before:

ruby 3.4.0dev (2024-04-23T16:59:11Z v3.4.0-pshopify-pr.. 70b931820e) +YJIT [arm64-darwin23]
Warming up --------------------------------------
              parse:    10.000 i/100ms
             render:    72.000 i/100ms
     parse & render:     8.000 i/100ms
Calculating -------------------------------------
              parse:     97.222 (± 1.0%) i/s   (10.29 ms/i) -    980.000 in  10.081357s
             render:    695.303 (± 2.7%) i/s    (1.44 ms/i) -      6.984k in  10.053073s
     parse & render:     81.088 (± 2.5%) i/s   (12.33 ms/i) -    816.000 in  10.069440s

After:

ruby 3.4.0dev (2024-04-23T16:59:11Z v3.4.0-pshopify-pr.. 70b931820e) +YJIT [arm64-darwin23]
Warming up --------------------------------------
              parse:    10.000 i/100ms
             render:    70.000 i/100ms
     parse & render:     8.000 i/100ms
Calculating -------------------------------------
              parse:    101.534 (± 0.0%) i/s    (9.85 ms/i) -      1.020k in  10.046007s
             render:    687.268 (± 1.3%) i/s    (1.46 ms/i) -      6.930k in  10.084962s
     parse & render:     84.576 (± 2.4%) i/s   (11.82 ms/i) -    848.000 in  10.033386s

This PR improves the parsing speed by ~4%

[ggmichaelgo]

I should use byteslice here instead of creating a range