debt: Ditch `core.ps1`

[Ash258]

• [x] Drop Reset-Alias
• [ ] Circular deps
• [ ] core.ps1 -> init.ps1/bootstrap.ps1 and real core functions
  • Bootstrap will be executed only in:
    • test init?
    • scoop.ps1
    • binaries
• [ ] Replace all dot sourcing with check:

@(
    @('manifest', 'manifest_path'),
    @('Helpers', 'Test...')
) | ForEach-Object {
    if (!(Get-Command $_[1] -ErrorAction 'SilentlyContinue')) {
         . (Join-Path $PSScriptRoot "..\lib\${_}.ps1")
    }
}