NewPP pretty printer library added to branch newpp

[dmacqueen]

Description

Added the directory compiler/Basics/newpp with the code for the new pretty printer library (NewPP: NEW_PP).
Replaced old pretty printers for plambda, flint, and cps IRs and FLINT types (Lty.tyc and Lty.lty), and replaced calls of
the old pretty printers in many files under the directories FLINT and CPS and NewCodeGen). Also some minor changes
relating to or preparing for future work on FLINT and its bugs.

Related Issue

Don't know.

Motivation and Context

New pretty printer library is much easier to use.

How Has This Been Tested?

Testing is in progress.

[spdegabrielle]

Are all these commits meant to be in this PR?

The newpp branch was created for work on the new PrettyPrint library, which has been concluded. However a "pull" or merge with the main branch has been delayed for several months, and in the meantime I have been working on (1) completing and rationalizing the CM library architecture of the compiler, which has resulted in adding missing CM description files, such as FLINT/flint.cm, and editing some of the old CM description files, such as core.cm, which will probably go away in the end. More recently I have been making changes (in new copies of source files) to begin to "clarify" and "simplify" CM itself (e.g in cm/paths/dbm). I agree, the newpp branch is quite overdue for merging into main.

With 304 commits in this PR - isn't it going to get harder and harder to merge the longer it is left?

I initially thought 'oh its ok this branch is temporarily main' - but the main branch is actively getting updates too.

I'm not very experienced in this so please forgive me if I have misunderstood.