add more APIs to compiler/debugutils; re-export it (#18243)

tests/compiler/tdebugutils.nim

@@ -0,0 +1,38 @@
+discard """
+  joinable: false
+  disabled: true
+"""
+
+#[
+This test illustrates some features of `debugutils` to debug the compiler.
+
+## example
+this shows how to enable compiler logging just for a section of user code,
+without generating tons of unrelated log messages for code you're not interested
+in debugging.
+
+```sh
+# enable some debugging code, e.g. the `when false:` block in `semExpr`
+nim c -o:bin/nim_temp --stacktrace -d:debug -d:nimDebugUtils compiler/nim
+bin/nim_temp c tests/compiler/tdebugutils.nim
+```
+
+(use --filenames:abs for abs files)
+
+## result
+("<", "tdebugutils.nim(16, 3)",  {.define(nimCompilerDebug).}, nil)
+(">", "tdebugutils.nim(17, 3)", let a = 2.5 * 3, {}, nkLetSection)
+(">", "tdebugutils.nim(17, 15)", 2.5 * 3, {efAllowDestructor, efWantValue}, nkInfix)
+(">", "tdebugutils.nim(17, 11)", 2.5, {efAllowStmt, efDetermineType, efOperand}, nkFloatLit)
+("<", "tdebugutils.nim(17, 11)", 2.5, float64)
+(">", "tdebugutils.nim(17, 17)", 3, {efAllowStmt, efDetermineType, efOperand}, nkIntLit)
+("<", "tdebugutils.nim(17, 17)", 3, int literal(3))
+("<", "tdebugutils.nim(17, 15)", 2.5 * 3, float)
+("<", "tdebugutils.nim(17, 3)", let a = 2.5 * 3, nil)
+(">", "tdebugutils.nim(18, 3)",  {.undef(nimCompilerDebug).}, {}, nkPragma)
+]#
+
+proc main =
+  {.define(nimCompilerDebug).}
+  let a = 2.5 * 3
+  {.undef(nimCompilerDebug).}