[Legacy Support] tsc --watch should NOT clear my console

[roblav96]

tldr;

Please merge this:
#21303 Added --preserveWatchOutput flag
🍰

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After upgrading to typescript@2.7.1 my terminal gets cleared whenever the watcher detects a change.

This is painfully annoying because I have a vertical widescreen monitor setup and my eyes naturally focus to the bottom.

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#20389 "tsc --watch should clear screen on new compilation" Two: Electric Boogaloo
#20427 Added console clearing with a message to --watch starts
#21295 Allow not clearing the console on recompiles in --pretty --watch mode

[mhegazy]

Duplicate of #21295

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.