Optional args fixed

[swamishiju]

Sister PR lfortran/lfortran#6985

[swamishiju]

I removed a C-test for def_func_01 it seems to be giving some error related to strings but integration tests run fine for me locally.

[certik]

Is there a reason you had to merge "main" of LFortran into the libasr? That pulls in a lot of unrelated changes. If it is needed, then we need to first update libasr in a separate PR. I have done that here: #2850 But it shouldn't be needed, at least in LPython the CI should work with just your simple change. In LFortran the CI might fail without the merge, so there we might need to merge it. Ultimately to get this change in, we do need to update the libasr anyway. The good news is that it seems to be very simple now.

[swamishiju]

I dont think its needed i was facing some weird bugs i fixed later but i dont think the merge was needed. First time using submodules like this bit messy im sry ill open new PRs