feat: add C ndarray interface and refactor implementation for stats/base/dmeanpn

[gururaj1512]

---

type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:

• task: lint_filenames
  status: passed
• task: lint_editorconfig
  status: passed
• task: lint_markdown
  status: passed
• task: lint_package_json
  status: na
• task: lint_repl_help
  status: passed
• task: lint_javascript_src
  status: passed
• task: lint_javascript_cli
  status: na
• task: lint_javascript_examples
  status: na
• task: lint_javascript_tests
  status: passed
• task: lint_javascript_benchmarks
  status: passed
• task: lint_python
  status: na
• task: lint_r
  status: na
• task: lint_c_src
  status: missing_dependencies
• task: lint_c_examples
  status: missing_dependencies
• task: lint_c_benchmarks
  status: na
• task: lint_c_tests_fixtures
  status: na
• task: lint_shell
  status: na
• task: lint_typescript_declarations
  status: passed
• task: lint_typescript_tests
  status: na
• task: lint_license_headers
  status: passed

---

Resolves None

Description

What is the purpose of this pull request?

This pull request:

• adds C ndarray interface for stats/base/dmeanpn
• refactors JavaScript implementation
• refactors tests, docs, benchmarks and examples.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves None

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

---

@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dmeanpn	$379/379$ $+100.00\mathrm{\%}$	$18/18$ $+100.00\mathrm{\%}$	$4/4$ $+100.00\mathrm{\%}$	$379/379$ $+100.00\mathrm{\%}$

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

[kgryte]

LGTM after clean-up.