perf: regex ID_START and ID_CONTINUE only if necessary

[nigrosimone]

Performance improvements mainly on complex patterns; simple/static paths unaffected

PR

 ✓ src/index.bench.ts 4841ms
     name                      hz     min      max    mean     p75     p99    p995    p999     rme  samples
   · static path     4,538,328.18  0.0001  11.2277  0.0002  0.0002  0.0004  0.0005  0.0011  ±4.47%  2269165
   · simple path       891,101.29  0.0009   0.3554  0.0011  0.0011  0.0014  0.0016  0.0065  ±0.33%   445551
   · multi segment       2,603.09  0.3296   0.9718  0.3842  0.4037  0.6521  0.7309  0.8408  ±0.86%     1302
   · multi pattern       5,371.88  0.1749   0.8692  0.1862  0.1839  0.2858  0.3067  0.3851  ±0.46%     2686
   · tricky pattern      3,583.51  0.2616   0.6453  0.2791  0.2826  0.4156  0.4443  0.5134  ±0.45%     1792
   · asterisk            2,367.19  0.3640   1.1230  0.4224  0.4339  0.7590  0.8449  0.9435  ±1.02%     1184

MASTER

 ✓ src/index.bench.ts 4785ms
     name                      hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · static path     4,624,035.08  0.0001  4.0280  0.0002  0.0002  0.0004  0.0005  0.0010  ±1.74%  2312018
   · simple path       832,855.50  0.0009  0.2727  0.0012  0.0012  0.0021  0.0028  0.0105  ±0.33%   416428
   · multi segment       2,643.93  0.3361  1.0880  0.3782  0.3700  0.6418  0.7283  0.8704  ±0.83%     1322
   · multi pattern       4,925.40  0.1749  0.3692  0.2030  0.2183  0.3142  0.3219  0.3535  ±0.65%     2463
   · tricky pattern      2,994.94  0.2687  0.8679  0.3339  0.3428  0.5811  0.6230  0.8570  ±0.95%     1498
   · asterisk            2,177.35  0.3793  1.0258  0.4593  0.4764  0.7601  0.7994  0.8557  ±0.87%     1089

static path

• PR: 4.538M ops
• MASTER: 4.624M ops (~+1.8%)

simple path

• PR: 891k (~+7%) 🚀
• MASTER: 832k

multi segment

• PR: 2,603
• MASTER: 2,643 (~+1.5%)

multi pattern

• PR: 5,371 (~+9%) 🚀
• MASTER: 4,925

tricky pattern

• PR: 3,583 (~+19%) 🚀🔥
• MASTER: 2,994

asterisk

• PR: 2,367 (~+8–9%) 🚀
• MASTER: 2,177