name_cache implement symbolize_names support

Also micro optimize a bit further.

```
== Parsing activitypub.json (58160 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json   832.000 i/100ms
                  oj   799.000 i/100ms
          Oj::Parser   969.000 i/100ms
           rapidjson   636.000 i/100ms
Calculating -------------------------------------
                json      8.020k (± 0.3%) i/s  (124.70 μs/i) -     40.768k in   5.083607s
                  oj      7.942k (± 1.7%) i/s  (125.92 μs/i) -     39.950k in   5.031909s
          Oj::Parser      9.515k (± 4.4%) i/s  (105.10 μs/i) -     47.481k in   5.001202s
           rapidjson      6.282k (± 2.1%) i/s  (159.20 μs/i) -     31.800k in   5.064719s

Comparison:
                json:     8019.6 i/s
          Oj::Parser:     9514.5 i/s - 1.19x  faster
                  oj:     7941.9 i/s - same-ish: difference falls within error
           rapidjson:     6281.6 i/s - 1.28x  slower

== Parsing twitter.json (567916 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json    67.000 i/100ms
                  oj    62.000 i/100ms
          Oj::Parser    79.000 i/100ms
           rapidjson    55.000 i/100ms
Calculating -------------------------------------
                json    670.935 (± 2.7%) i/s    (1.49 ms/i) -      3.417k in   5.096850s
                  oj    618.937 (± 3.2%) i/s    (1.62 ms/i) -      3.100k in   5.014800s
          Oj::Parser    768.894 (± 1.7%) i/s    (1.30 ms/i) -      3.871k in   5.036093s
           rapidjson    556.882 (± 2.7%) i/s    (1.80 ms/i) -      2.805k in   5.040970s

Comparison:
                json:      670.9 i/s
          Oj::Parser:      768.9 i/s - 1.15x  faster
                  oj:      618.9 i/s - 1.08x  slower
           rapidjson:      556.9 i/s - 1.20x  slower

== Parsing citm_catalog.json (1727030 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json    35.000 i/100ms
                  oj    32.000 i/100ms
          Oj::Parser    43.000 i/100ms
           rapidjson    39.000 i/100ms
Calculating -------------------------------------
                json    382.262 (± 2.6%) i/s    (2.62 ms/i) -      1.925k in   5.039336s
                  oj    348.721 (± 0.6%) i/s    (2.87 ms/i) -      1.760k in   5.047265s
          Oj::Parser    478.294 (± 0.6%) i/s    (2.09 ms/i) -      2.408k in   5.034798s
           rapidjson    398.740 (± 0.8%) i/s    (2.51 ms/i) -      2.028k in   5.086365s

Comparison:
                json:      382.3 i/s
          Oj::Parser:      478.3 i/s - 1.25x  faster
           rapidjson:      398.7 i/s - 1.04x  faster
                  oj:      348.7 i/s - 1.10x  slower
```

Author: byroot