Read tests from the file system

[Willem3141]

It would be much nicer if tests, instead of being hard-coded into the binary, would be read from /var/tests at runtime. A file would then contain a series of tests which are executed by the test runner.

• Decide a binary format for tests (KEXC, or just binary code without a header or something?)
• Implement getting a list of tests to execute
• Implement reading and calling a test

[ddevault]

I think that loading KEXC files from /var/tests/ would be a good idea. We could have a custom KEXC header that lists tests and such, i.e.

#include "kernel.inc"
#include "tests.inc"
.db "KEXC"
.db KEXC_TEST_TABLE
.dw tests
.db KEXC_HEADER_END

tests:
    .dw test_1, test_1_name
    .dw test_2, test_2_name
    .dw test_3, test_3_name

test_1_name:
    .db "Test 1", 0
test_1:
    assert(1)
    ; ...
    ret

; ...