This patch contains some compile time perf improvements.
@ahejlsberg recently implemented tail call elimination for recursive conditional types (microsoft/TypeScript#45711). This release is preparation work to take advantage of this new feature by making most type helper functions tail recursive. From the non scientific tests I made on my machine, this also improves the compilation time of the tests/ folder quite significantly on our current TS version (4.4). Compilation is ~ 20% faster.