feat: add support for accessor arrays and refactor stats/base/variancetk

[prajjwalbajpai]

Resolves #5690.

Description

This pull request:

• Refactors and adds protocol support to stats/base/variancetk as described in the issue.

• Read, understood, and followed the contributing guidelines

---

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/variancetk	$\color{green}267/267$ $\color{green}+100.00\%$	$\color{green}17/17$ $\color{green}+100.00\%$	$\color{green}3/3$ $\color{green}+100.00\%$	$\color{green}267/267$ $\color{green}+100.00\%$

The above coverage report was generated for the changes in this PR.

[prajjwalbajpai]

@aayush0325 please review

[kgryte]

LGTM