Optimize Ext::Generator::State#configure

If we assume that most of the time the `opts` hash is small
it's faster to go over the provided keys with a `case` than
to test all possible keys one by one.

Before:

```
== Encoding small nested array (121 bytes)
ruby 3.4.0preview2 (2024-10-07 master 32c733f57b) +YJIT +PRISM [arm64-darwin23]
Warming up --------------------------------------
                json   156.832k i/100ms
                  oj   209.769k i/100ms
           rapidjson   162.922k i/100ms
Calculating -------------------------------------
                json      1.599M (± 2.5%) i/s  (625.34 ns/i) -      7.998M in   5.005110s
                  oj      2.137M (± 1.5%) i/s  (467.99 ns/i) -     10.698M in   5.007806s
           rapidjson      1.677M (± 3.5%) i/s  (596.31 ns/i) -      8.472M in   5.059515s

Comparison:
                json:  1599141.2 i/s
                  oj:  2136785.3 i/s - 1.34x  faster
           rapidjson:  1676977.2 i/s - same-ish: difference falls within error

== Encoding small hash (65 bytes)
ruby 3.4.0preview2 (2024-10-07 master 32c733f57b) +YJIT +PRISM [arm64-darwin23]
Warming up --------------------------------------
                json   216.464k i/100ms
                  oj   661.328k i/100ms
           rapidjson   324.434k i/100ms
Calculating -------------------------------------
                json      2.301M (± 1.7%) i/s  (434.57 ns/i) -     11.689M in   5.081278s
                  oj      7.244M (± 1.2%) i/s  (138.05 ns/i) -     36.373M in   5.021985s
           rapidjson      3.323M (± 2.9%) i/s  (300.96 ns/i) -     16.871M in   5.081696s

Comparison:
                json:  2301142.2 i/s
                  oj:  7243770.3 i/s - 3.15x  faster
           rapidjson:  3322673.0 i/s - 1.44x  faster
```

After:

```
== Encoding small nested array (121 bytes)
ruby 3.4.0preview2 (2024-10-07 master 32c733f57b) +YJIT +PRISM [arm64-darwin23]
Warming up --------------------------------------
                json   168.087k i/100ms
                  oj   208.872k i/100ms
           rapidjson   149.909k i/100ms
Calculating -------------------------------------
                json      1.761M (± 1.1%) i/s  (567.90 ns/i) -      8.909M in   5.059794s
                  oj      2.144M (± 0.9%) i/s  (466.37 ns/i) -     10.861M in   5.065903s
           rapidjson      1.692M (± 1.7%) i/s  (591.04 ns/i) -      8.545M in   5.051808s

Comparison:
                json:  1760868.2 i/s
                  oj:  2144205.9 i/s - 1.22x  faster
           rapidjson:  1691941.1 i/s - 1.04x  slower

== Encoding small hash (65 bytes)
ruby 3.4.0preview2 (2024-10-07 master 32c733f57b) +YJIT +PRISM [arm64-darwin23]
Warming up --------------------------------------
                json   242.957k i/100ms
                  oj   675.217k i/100ms
           rapidjson   355.040k i/100ms
Calculating -------------------------------------
                json      2.569M (± 1.5%) i/s  (389.22 ns/i) -     12.877M in   5.013095s
                  oj      7.128M (± 2.3%) i/s  (140.30 ns/i) -     35.787M in   5.023594s
           rapidjson      3.656M (± 3.1%) i/s  (273.50 ns/i) -     18.462M in   5.054558s

Comparison:
                json:  2569217.5 i/s
                  oj:  7127705.6 i/s - 2.77x  faster
           rapidjson:  3656285.0 i/s - 1.42x  faster
```

0 files changed, 0 insertions, 0 deletions