Tastydoc update

[abgruszecki]

Update Tastydoc so that it compiles again.

See #7668.

Remaining work: update collections to 2.13, update tasty.reflect usages in places where a bit of thinking is necessary (NOTE comments)

[nicolasstucki]

@AleksanderBG now it compiles. I did not try the tests.

[abgruszecki]

I generated the test documentation and there's definitely something wrong with the changes. Many links are broken. Seems some packages are treated as objects, probably we borked something when adjusting the SymRef code.

[bishabosha]

its still using the old syntax for givens e.g.

[error] -- [E019] Syntax Error: /Users/jamie/workspace/dotty/tastydoc/src/dotty/tastydoc/TastyExtractor.scala:61:153 
[error] 61 |  def extractClassMembers(reflect: Reflection)(body: List[reflect.Statement], symbol: reflect.ClassDefSymbol, parentRepresentation: Some[Representation]) given (mutablePackagesMap: scala.collection.mutable.HashMap[String, EmulatedPackageRepresentation]) : List[Representation with Modifiers] = {

[abgruszecki]

@bishabosha tastydoc compiles on this branch for me, have you pulled all the changes?

[bishabosha]

@AleksanderBG Sorry, I should have checked the commits here before commenting ha

[abgruszecki]

Apparently having tastydoc not compile breaks launchIDE, so I'm merging this PR into master. We'll worry about making Tastydoc work properly later on.