RFR JDK-8251213 [TESTBUG] CDS tests shouldn't write output files into test.classes directory

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8251213
http://cr.openjdk.java.net/~iklam/jdk16/8251213-cds-shouldnt-write-test-classes-dir.v01/

Many of the CDS tests would write output files to the directory
given by System.getProperty("test.classes").

I changed them to write to the scratch directory, i.e.,
System.getProperty("user.dir", "."). This way, it's easier to examine the
output of the tests.

Please start the review with CDSTestUtils.java.

I validated the change by going to the jtreg work directory and:

     $ find $(find . -name classes) -type f | grep -v '[.]class$' | wc -l
     0

(There used to be a lot of .jsa, .classlist, .stdout, etc).

Executed all the tests locally on Linux. Running mach5 tiers1-4.

Thanks
- Ioi