Rename -Y{cook|drop}-comments to -Y{cook|drop}-docs

These operate on documentation strings, not comments.

A comment is never cooked and always droped
```scala
// comment
```

Documentation can be cooked and may be dropped if not needed

```scala
/** documentation */
```

Author: nicolasstucki

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -177,8 +177,8 @@ trait AllScalaSettings extends CommonScalaSettings { self: Settings.SettingGroup
   val YshowPrintErrors: Setting[Boolean] = BooleanSetting("-Yshow-print-errors", "Don't suppress exceptions thrown during tree printing.")
   val YtestPickler: Setting[Boolean] = BooleanSetting("-Ytest-pickler", "Self-test for pickling functionality; should be used with -Ystop-after:pickler.")
   val YcheckReentrant: Setting[Boolean] = BooleanSetting("-Ycheck-reentrant", "Check that compiled program does not contain vars that can be accessed from a global root.")
-  val YdropComments: Setting[Boolean] = BooleanSetting("-Ydrop-comments", "Drop comments when scanning source files.")
-  val YcookComments: Setting[Boolean] = BooleanSetting("-Ycook-comments", "Cook the comments (type check `@usecase`, etc.)")
+  val YdropComments: Setting[Boolean] = BooleanSetting("-Ydrop-docs", "Drop documentation when scanning source files.", aliases = List("-Ydrop-comments"))
+  val YcookComments: Setting[Boolean] = BooleanSetting("-Ycook-docs", "Cook the documentation (type check `@usecase`, etc.)", aliases = List("-Ycook-comments"))
   val YforceSbtPhases: Setting[Boolean] = BooleanSetting("-Yforce-sbt-phases", "Run the phases used by sbt for incremental compilation (ExtractDependencies and ExtractAPI) even if the compiler is ran outside of sbt, for debugging.")
   val YdumpSbtInc: Setting[Boolean] = BooleanSetting("-Ydump-sbt-inc", "For every compiled foo.scala, output the API representation and dependencies used for sbt incremental compilation in foo.inc, implies -Yforce-sbt-phases.")
   val YcheckAllPatmat: Setting[Boolean] = BooleanSetting("-Ycheck-all-patmat", "Check exhaustivity and redundancy of all pattern matching (used for testing the algorithm).")