perf: reduce concatenation for optional properties

[gurgunday]

• Combines the comma and property name into one string when the schema is compiled

This results in one fewer concatenation per subsequent supplied property, repeated across every object

   Existing benchmark                                           Node 24    Node 26
  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━  ━━━━━━━━━  ━━━━━━━━━
   object with properties of different types                     +16.1%     +14.1%
  ───────────────────────────────────────────────────────────  ─────────  ─────────
   short array of objects with properties of different types      +1.4%      +8.8%

[mcollina]

lgtm

[Tony133]

lgtm