fix: resolve JavaScript lint failures in CI (no-new-array, n/no-unsupported-features, no-buffer-constructor)

[Planeshifter]

Summary

Fixes two of three persistent JavaScript lint failures identified in CI issue #11867:

• @stdlib/ndarray/fancy test (stdlib/no-new-array): Replace new Array(shape.length) with [] + push in test.instance.get_nd.js. The badValue helper is semantically equivalent — both produce an array of shape.length elements in the same order.

• @stdlib/symbol/async-iterator (n/no-unsupported-features/es-builtins): Add var Symbol = require('@stdlib/symbol/ctor'); to shadow the global Symbol. The eslint-plugin-n rule only flags the global Symbol.asyncIterator (requires Node ≥ 10); a local binding named Symbol resolves the rule without changing runtime behavior. This matches the established pattern in @stdlib/symbol/to-primitive.

Not fixed here

The third error — stale // eslint-disable-line no-buffer-constructor in @stdlib/utils/constructor-name/examples/index.js — was reverted from this PR. Removing that disable directive triggers a pre-existing stdlib/doctest failure caused by the RE_ANNOTATION regex greedily spanning the function noop() {} block (which contains no ; character). That issue requires a separate fix (either adding a ; inside noop's body to break the greedy match, or fixing the regex in the doctest rule). It will be addressed in a follow-up.

Test plan

• Verify CI JavaScript lint job passes on this branch
• Confirm @stdlib/symbol/async-iterator exports the correct Symbol.asyncIterator symbol in Node ≥ 10 environments and null in older environments
• Confirm @stdlib/ndarray/fancy get-nd tests still throw TypeError for out-of-bounds indices

Notes

• PR fix: resolve JavaScript lint errors (issue #11867) #11878 (by a contributor) addresses only one of these two errors (missing the ndarray/fancy test fix). This PR completes both.
• The symbol/iterator sibling still uses the bare global Symbol.iterator (predates this pattern); that is out of scope.

Contributing Guidelines

• Read, understood, and followed the contributing guidelines

https://claude.ai/code/session_01SUwbJqiL1Fu619Hgnkt78N

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Coverage Report

Package	Statements	Branches	Functions	Lines
ndarray/fancy	$\color{green}152/152$ $\color{green}+0.00%$	$\color{green}9/9$ $\color{green}+0.00%$	$\color{green}1/1$ $\color{green}+0.00%$	$\color{green}152/152$ $\color{green}+0.00%$
symbol/async-iterator	$\color{green}91/91$ $\color{green}+0.00%$	$\color{red}2/3$ $\color{green}+0.00%$	$\color{green}0/0$ $\color{green}+0.00%$	$\color{green}91/91$ $\color{green}+0.00%$

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