revert #20719; relieve std/assertions of the sysFatal dep

[ringabout]

revert #20719

ref https://github.com/nim-lang/Nim/pull/20718/files#r1010607801

I'm not sure whether import system/sysFatal works and the leaking is just a flaky when investigating #20718 . Better safe than sorry. I revert that PR and relieve std/assertions of the sysFatal dep following Nim/lib/std/syncio.nim

template sysFatal(exc, msg) =
  raise newException(exc, msg)

For the record, the leak was and I can reproduce it on wsl2.

==99591== HEAP SUMMARY:
==99591==     in use at exit: 10 bytes in 1 blocks
==99591==   total heap usage: 32 allocs, 31 frees, 5,113 bytes allocated
==99591== 
==99591== 10 bytes in 1 blocks are definitely lost in loss record 1 of 1
==99591==    at 0x483DD99: calloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==99591==    by 0x10CE14: alloc0Impl__system_1765 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10CE42: allocShared0Impl__system_1778 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10F091: prepareAdd (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10F3F3: setLengthStrV2 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10ACD9: addChars__stdZprivateZdigitsutils_100 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10B31B: addIntImpl__stdZprivateZdigitsutils_59 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10B3C7: addInt__stdZprivateZdigitsutils_150 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10B637: addInt__stdZprivateZdigitsutils_153 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10C608: addInt__stdZprivateZdigitsutils_175 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x10C6A9: dollar___systemZdollars_8 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591==    by 0x111608: raiseFieldError2 (in /home/vsts/work/1/s/tests/arc/tcaseobj)
==99591== 
==99591== LEAK SUMMARY:
==99591==    definitely lost: 10 bytes in 1 blocks
==99591==    indirectly lost: 0 bytes in 0 blocks
==99591==      possibly lost: 0 bytes in 0 blocks
==99591==    still reachable: 0 bytes in 0 blocks
==99591==         suppressed: 0 bytes in 0 blocks
==99591== 
==99591== For lists of detected and suppressed errors, rerun with: -s
==99591== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

[ringabout]

It was actually

when not declared(sysFatal):
  include "system/fatal"

before. I think it is better to do what std/syncio did, which was done years ago.

[github-actions]

Thanks for your hard work on this PR!
The lines below are statistics of the Nim compiler built from 12a20b9

Hint: mm: orc; opt: speed; options: -d:release
164620 lines; 6.811s; 613.938MiB peakmem