Communicate the error name when a test fails

[mororo250]

Hi everyone this is my first pr. Glad to be able to start contributing here
Closes #14972

Before:

zig build test -Doptimize=ReleaseFast
test
└─ run test 0/1 passed, 1 failed
error: 'main.test.oops' failed
error: while executing test 'main.test.oops', the following test command failed:
./.zig-cache/o/ba87fa3c0cdf82f2e19b301925405ea7/test --cache-dir=./.zig-cache --seed=0x546c018b --listen=-

Build Summary: 3/5 steps succeeded; 1 failed; 0/1 tests passed; 1 failed

After:

zig build test -Doptimize=ReleaseFast
test
└─ run test 0/1 passed, 1 failed
error: 'main.test.oops' failed with error TestUnexpectedResult
error: while executing test 'main.test.oops', the following test command failed:
./.zig-cache/o/178c7f9c32f856400a1065693d5b5d73/test --cache-dir=./.zig-cache --seed=0xc25908be --listen=-

Build Summary: 3/5 steps succeeded; 1 failed; 0/1 tests passed; 1 failed 

[mororo250]

I will add a link to #15520 from @Parzival-3141 who had a closed pr linked very similar to this one.