Put back withPromptPaused, but make it private[mill]

[lihaoyi]

Turns out we still need it for console and repl commands in order to disable the prompt auto updater thread. But we can limit its use to only within EvaluatorCore for every exclusive command, rather than letting it be used in any random user-land task

Also refactors it such that exclusive = true commands use SystemStreams.original by default, allowing def repl and def console to work without overriding the system streams themselves

Tested manually

$ ./mill -i dist.launcher && (cd example/scalalib/basic/1-simple  && ../../../../out/dist/launcher.dest/run -i path compile sources + console + version)

[2579/2579] ========================================================================= dist.launcher ============================================================================= 2s
[5/57] path
sources
allSources
allSourceFiles
compile
[56/57] console
Welcome to Scala 2.13.11 (OpenJDK 64-Bit Server VM, Java 17.0.6).
Type in expressions for evaluation. Or try :help.

scala> 1 + 1
val res0: Int = 2

scala> :quit
[57/57] version
0.12.0-RC2-65-906911
[57/57] =============================================================== path compile sources + console + version ================================================================ 7s
lihaoyi mill$

[lefou]

Do we still print rhe task id and the task name before the exclusive task output? This would be especially helpful in case multiple exclusive tasks run sequentially.

[lihaoyi]

@lefou yes, it looks like this:

$ ./mill -i dist.launcher && (cd example/scalalib/basic/1-simple  && ../../../../out/dist/launcher.dest/run -i path compile sources + console + version)

[2579/2579] ========================================================================= dist.launcher ============================================================================= 2s
[5/57] path
sources
allSources
allSourceFiles
compile
[56/57] console
Welcome to Scala 2.13.11 (OpenJDK 64-Bit Server VM, Java 17.0.6).
Type in expressions for evaluation. Or try :help.

scala> 1 + 1
val res0: Int = 2

scala> :quit
[57/57] version
0.12.0-RC2-65-906911
[57/57] =============================================================== path compile sources + console + version ================================================================ 7s
lihaoyi mill$

[lefou]

Great.