SI-8512 Infer a type for f"$args"

The f-interpolator gets a type param that better be Any to avoid
unfortunate widenings.

Hey, it worked!

Unfortunately, when `Any` is inferred, `-Xlint:infer-any` takes notice.

This is probably a greater problem for the f-interpolator than for
quasiquotes, which are a more specialized tool.
SI-8512 Infer Any for the q

Avoid the widening bug for q.  This resolution also suffers
from the inference of Any, which can trigger a warning and
an anxiety attack.  But that's still better than doing the
wrong thing.

Right?
Merge pull request #3909 from som-snytt/issue/8512

SI-8512 Infer a type for f"$args"
Set currentUnit while generating bytecode.
Comment clarification in GenASM
Remove Tracked, add type information to ClassBType

Before this change, a ClassBType was just a name. The `exemplars` map
stored a Tracked instance for every ClassBType. Tracked stored
type information that is required later in the backend when things
may run concurrently. In particular: superclass, interfaces, flags
and information for emitting the InnerClass attribute. Now we put all
the information stored in Tracked directly in the ClassBType.

There is still one hash map: `classBTypeFromInternalNameMap` maps
a JVM internal class name (e.g. "scala/Predef$") to the corresponding
ClassBType. This map is used during bytecode generation, when the
ASM framework computes stack map frames.

In order to compute stack map frames, the ASM framework needs to be
able to get the LUB of two types. The default implementation uses
reflection to get type information, however that doesn't work in our
case: the classes we compile are not on the classpath. So instead,
the backend overwrites the method `getCommonSuperClass` of the
ClassWriter. This method receives two class internal names and
computes their LUB. This is done by looking up the ClassBTypes in the
`classBTypeFromInternalNameMap` and invoking `jvmWiseLUB`.
Add the ACC_DEPRECATED flag in javaFlags, instead of each call site.
minor review cleanups
coreBTypes as component wip
fix indentation in delambdafy
Don't traverse all trees in delambdafy phase if delambdafy:inline
Fix InnerClass / EnclosingMethod attributes
small cleanup in assertions