Overhaul and simplify TPrint implementation

[lihaoyi]

Fixes com-lihaoyi/Ammonite#221
Fixes com-lihaoyi/Ammonite#629
Fixes com-lihaoyi/Ammonite#670
Fixes #45
Fixes #44

The old TPrint implementation did a clever thing where it allowed a user to over-ride the TPrinting of a given type by providing an appropriate implicit. While that worked in most cases, it was fiendishly complex, and the intricate nesting of implicit resolution and macro resolution ended up providing and endless source of hard to resolve bugs.

This new implementation is much simpler and less flexible: we simply walk the type data structure in the macro, and spit out a colored fansi.Str with the type names hard-coded to fansi.Green. The only runtime support necessary is in the def recolor function, which parses the incoming fansi.Str and replaces the hardcoded fansi.Green colors with whatever is specified by the implicit TPrintColors. As implicits cannot be used to override tprinting anymore, we now have hardcoded support for tprinting functions and tuples.

While the old macro generated a complex tree of Scala function calls that is evaluated to generate the output fansi.Str at runtime, the new macro simply spits out a single fansi.Str that is serialized into a java.lang.String and deserialized back into a fansi.Str for usage at runtime. We propagate a WrapType enumeration up the recursion, to help the callers decide if they need to wrap things in parens or not.

This gives up a bit of flexibility, but AFAIK nobody was really using that flexibility anyway. In exchange, we fix a whole bunch of long-standing bugs, and have a drastically simpler implementation.

The fixed bugs are covered by regression unit tests added to TPrintTests.scala. All existing tests also pass, so hopefully that'll catch any potential regressions. There's probably more bugs where we're not properly setting or handling the WrapType, but exhaustively testing/surfacing/fixing all of those is beyond the scope of this PR. For now, I just kept the current set of tests passing.

Managed to get the Scala3 side working. I didn't realize how half-baked the Scala3 implementation of TPrint is; so much of the Scala2 functionality just isn't implemented and doesn't work. Nevertheless, fixing that is beyond the scope of this PR. I just kept it green with the existing set of green tests passing (except for the custom tprinter test, which is no longer applicable)

Review by @lolgab.

[lihaoyi]

Also perhaps worth a review by @alexarchambault since this is primarily used in Ammonite

[lolgab]

Some weird formatting happening here

[lihaoyi]

fixed this bit of weird formatting

[lolgab]

I'm not a macro expert, but nothing seems wrong to me.
Also, this fixes a lot of open bugs, and every test passes.

LGTM! 👍 Thank you!