Check for platform-dependent path usage

As suggested by @SteveL-MSFT.

A rule that checks/corrects filesystem path usage that doesn't translate across between Windows and UNIX-like OSes could ease migration to PowerShell Core.

User story

As a PowerShell user, I want a rule to tell me when a path I've used
will break my script on another platform, so that I can write
cross-platform scripts more easily (e.g. for Azure scenarios).

Proposed technical implementation

Check all *-*Item and *-Path cmdlets (and their aliases) for direct string/bareword arguments to check for platform specific usages (like C:), or even encourage usage of Join-Path or [System.IO.Path]::Combine() instead of / and \.

Of course this check isn't universally feasible, but this is another case where some constant folding would come in handy for PowerShell analysis (something PSES could also use).

Latest current version of PSSA

1.17.1

The issue does not name files, tests, or an existing rule entry point. Start by reviewing how PSScriptAnalyzer implements rules and how it identifies *-Item and *-Path cmdlets and aliases. Define the supported platform-specific patterns and constant-folding scope before implementing; done means the rule detects and, if supported, corrects agreed cases with tests.