Instead of the "Display all <n> possibilities (y/n)" prompt, make MenuComplete use in-place paging to show completions that exceed the -CompletionQuery threshold

[mklement0]

Description of the new feature/enhancement

When a given tab completion invoked via the MenuComplete function yields more items than the threshold specified via Set-PSReadLineOption -CompletionQueryItems <n> (default is 100), the tab-completion UX changes fundamentally:

• Instead of completions, a Display all <n> possibilities (y/n) prompt is shown, which is itself somewhat disruptive.
• On opting in, the following UX benefits are lost, because a static list is printed before the command being edited is redisplayed:
  • Interactive, live filtering of completions as you type.
  • Additional information about the currently selected item in a separate line below the completions (what Show ToolTip when completions exceed CompletionQueryItems #1844 refers to as ToolTips).

A real-life example of where this would be useful is to enable the -Encoding parameters to then offer all available encodings (consistent with the parameter type), without detriment to those users only interested in the PowerShell-defined ones - see #1844

Proposed technical implementation details (optional)

• Never show the Display all <n> possibilities (y/n) prompt.
• Instead, provide in-place paging that preserves the UX benefits.

Loosely speaking, MenuComplete could act like the more or less utilities, only confined to the portion of the screen that fits -CompletionQueryItems values or as much as will fit on a single screen (with room for the "ToolTip" line).

PgUp / PgDown, which already work among the items shown on the one and only "page", could be used for paging (whereas Home and End act on the command line being edited).