fix(node-cache): Fixing issues with metrics reporting

[jmjones88]

Please check if the PR fulfills these requirements

• Followed the Contributing guidelines and Code of Conduct
• Tests for the changes have been added (for bug fixes/features) with 100% code coverage.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
This MR fixes multiple metrics-accounting issues that caused inaccurate ksize and vsize reporting over time.

The changes ensure that:

• Overwriting existing keys does not inflate size metrics.
• take() correctly removes keys even when cached values are falsy.
• NodeCacheStore correctly decrements value-size metrics for undefined values on overwrite, delete, and expiry.

[gemini-code-assist]

Code Review

This pull request optimizes the node-cache package by introducing an in-memory _values map in NodeCacheStore to track cached values synchronously, preventing redundant asynchronous lookups and fixing stats inflation during key overwrites. It also updates the take() method to support falsy values and adds comprehensive tests. The reviewer feedback highlights two critical issues: first, using this.store.has() in take() can incorrectly identify expired keys as existing, leading to premature deletion when deleteOnExpire is disabled; second, checking result !== undefined in the store's retrieval logic fails when a cached value is explicitly set to undefined, which can cause memory leaks. Code suggestions are provided to address both issues.

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