Fix stats overcounting on key updates in set/mset methods

[Copilot]

The set and mset methods unconditionally incremented the stats count, causing overcounting when updating existing keys instead of creating new ones.

Changes

• set method: Check key existence via keyv.has() before incrementing count
• mset method: Batch check keys via keyv.hasMany() and increment count only for new keys
• take method: Fix incorrect method names (recordHit/recordMiss → incrementHits/incrementMisses)

Example

const store = new NodeCacheStore({ maxKeys: 10 });
await store.set("foo", "bar");  // count: 1
await store.set("foo", "baz");  // count: 1 (not 2)

await store.mset([
  { key: "a", value: "1" },
  { key: "b", value: "2" }
]);  // count: 3

await store.mset([
  { key: "a", value: "updated" },  // existing
  { key: "c", value: "3" }         // new
]);  // count: 4 (not 5)

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