Move prompt to the top/bottom of the terminal

Instead of repeating the prompt on every line, display the prompt only at the top/bottom of the terminal.

This is how it works now (the top/bottom lines denote terminal window boundary):

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~/git/extern/reedline                                                     12/05/2021 12:48:28 AM
〉foo
Our buffer: foo

~/git/extern/reedline                                                     12/05/2021 12:48:30 AM
〉bar
Our buffer: bar

~/git/extern/reedline                                                     12/05/2021 12:48:33 AM
〉baz
Our buffer: baz





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This is what I suggest:

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〉foo
Our buffer: foo

〉bar
Our buffer: bar

〉baz
Our buffer: baz







~/git/extern/reedline                                                     12/05/2021 12:48:33 AM
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Of course, this should be configurable.

Disadvantage of this is that you won't see the previous prompts so you cannot check e.g. what directory you were when running "foo". Whether this matters or not I think depends on personal preference.

Review the issue discussion and the terminal prompt behavior in Reedline. Determine where prompt placement and its configuration are handled, then verify that prompts can be shown at the terminal top or bottom without repeating earlier prompts and that the choice is configurable.