Add new sanitazing to verification of stacktraces

Now stacktraces have additional substrings, separated by a slash:

  java-base/java.util.lang

They are stripped away.

Also, the placement of tabs has changed, and so the tabs are also
completely removed.

Author: dkhalanskyjb

kotlinx-coroutines-debug/test/StracktraceUtils.kt

@@ -11,6 +11,8 @@ public fun String.trimStackTrace(): String =
     trimIndent()
         .replace(Regex(":[0-9]+"), "")
         .replace(Regex("#[0-9]+"), "")
+        .replace(Regex("(?<=\tat )[^\n]*/"), "")
+        .replace(Regex("\t"), "")
         .applyBackspace()
 
 public fun String.applyBackspace(): String {