fix: req.query returns object instead of array for >20 repeated values

[IshitaSingh0822]

Fixes #7147
qs defaults arrayLimit to 20. When a repeated query param has more
than 20 values, qs returns a plain object with numeric string keys
instead of an array, silently breaking Array.isArray(), .forEach(),
.map() etc.

Fix: set arrayLimit: Infinity in parseExtendedQueryString(). The
existing parameterLimit (default 1000) already caps total query
string size, so there is no DoS risk.

[krzysdz]

The existing parameterLimit (default 1000) already caps total query string size, so there is no DoS risk.

parameterLimit restricts the number of parameters, but the original meaning (even before qs 6.14.1) of arrayLimit has been protection from sparse array creation such as ?arr[99999]=x. Removing this limit, allows creation of huge sparse arrays with just a single parameter.

There's already another PR that tries to solve this problem - #7151. I'll close this as a duplicate.

Please include only relevant changes in PRs. GitHub shows commits that were a part of #7037 as new changes here.