base: Change the unit test binary names to use .test, and to be consistent.

base: Change the unit test binary names to use .test, and to be consistent.

Most tests were named *test where * was the base name of the file being
tested, but some were named differently based on, for instance, the
name of the class that file implemented.

This change makes all the test names consistently based off of the file
name they test, and also brings in the new .test convention to make
them easier to read.

Now, if you have a file like fiber.cc you want to test, you'd have a
unit test in a file called fiber.test.cc, and a test called fiber.test
which would generate a binary called fiber.test.opt, fiber.test.debug,
etc.

Change-Id: I61d59016090371a9bae72066e7473a34aecea21f
Reviewed-on: https://gem5-review.googlesource.com/c/14677
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>