Fix #8020: Create dotty-tasty-inspector library

[nicolasstucki]

Repeats the changes in #7080 for dotty-tasty-inspector.

Extract the tasty-consumer out of the standard library and compiler.

• Create dotty-tasty-inspector project that depends on dotty-compiler
• Add missing test infrastructure dependencies on the dotty-tasty-inspector project or jar
• Refactored tasty.file.{ConsumeTasty, TastyConsumer}, TastyConsumerPhase, andTastyFromClass into dotty-tasty-inspector as TastyInspector
• Implement ConsumeTasty.apply directly (instead of as a java reflection call) as TastyInspector.inspect
• Now projects need to depend on "ch.epfl.lamp" %% "dotty-tasty-inspector" % scalaVersion.value
• Factored out dotty.tools.dotc.util.ClasspathFromClassloader core logic for dotty-staging and dotty-tasty-consumer
• Enabled tastdoc tests on CI (mostly to check it compiles)

[smarter]

What's the benefit of having an extra library instead of having this stuff in dotty-compiler ?

[nicolasstucki]

Same as in dotty-staging. Users that depend on this should not have access or care about the compiler.

[smarter]

To make things simpler we could fusion dotty-staging and dotty-tasty-consumer then.

[nicolasstucki]

dotty-staging and dotty-tasty-consumer are completely different libraries. There is probably no use-case where both would be combined. They mostly share a common way the build must be set up for them.

[nicolasstucki]

I'm considering renaming it tasty-inspector. What WDYT @smarter ?

Made requested changes