[1.x] Handle parsing of non-problems in JavaErrorParser

[Friendseeker]

Issue

JavaErrorParser assumes javac outputs start with a list of problems or notes. However in certain situations javac emits the following lines first

Loading source file D:\Repos\zinc\internal\zinc-compile-core\target\jvm-2.13\test-classes\sbt\internal\inc\javac\test1.java...
Constructing Javadoc information...

which is neither problems nor notes. The parser then gives up and parse nothing. Hence JavaCompilerSpec fails.

Fix

We explicitly match for lines that start with "Loading source file" or "Constructing Javadoc information" and skip these lines before parsing problems / notes.

Validating the fix

I tested on a Java 17 windows machine that emits the below during JavaCompilerSpec

Loading source file D:\Repos\zinc\internal\zinc-compile-core\target\jvm-2.13\test-classes\sbt\internal\inc\javac\test1.java...
Constructing Javadoc information...
D:\Repos\zinc\internal\zinc-compile-core\target\jvm-2.13\test-classes\sbt\internal\inc\javac\test1.java:14: error: class Test is public, should be declared in a file named Test.java
public class Test {
       ^
D:\Repos\zinc\internal\zinc-compile-core\target\jvm-2.13\test-classes\sbt\internal\inc\javac\test1.java:15: error: cannot find symbol
    public NotFound foo() { return 5; }
           ^
  symbol:   class NotFound
  location: class Test
2 errors

The test passed locally.

Closes #1451

[eed3si9n]

Could you add test for this plz? - https://github.com/sbt/zinc/blob/1.10.x/internal/zinc-compile-core/src/test/scala/sbt/internal/inc/javac/javaErrorParserSpec.scala

[Friendseeker]

@eed3si9n Addressed PR feedback & added test!