Local cache for `.nupkg` like other package managers

Summary of the new feature / enhancement

It could be useful with a local cache of downloaded .nupkg files, like other package managers does.

• Bun: https://bun.com/docs/pm/global-cache
• Chocolatey: https://docs.chocolatey.org/en-us/choco/commands/cache/
• Scoop: https://github.com/ScoopInstaller/Scoop/blob/master/libexec/scoop-cache.ps1

Having this would make it feasible to implement other fatures too, like:

• https://github.com/PowerShell/PSResourceGet/issues/1646

Proposed technical implementation details (optional)

• Make it optional.
• Make cache invalidation / deletion / purge logic configurable.
  • Keep to latest version of each script/module?
  • Delete cached items after x days?
• Could help with cache in CI/CD too, like in GitHub actions, if Install-Package did not delete the .nupkg files it downloaded.
• Add some cmdlets to manage cache
  • Get current cached items and total size.
  • Clear cache.

Start by reviewing the proposed local .nupkg cache behavior and the linked PSResourceGet issue 1646. Compare the referenced Bun, Chocolatey, and Scoop cache approaches, then define the optional caching, invalidation, purge, CI/CD behavior, and cache-management cmdlets needed for a complete design.