[compiler-rt][builtins] Add more test cases for __div[sdt]f3 LibCalls

* Make the three tests look more uniformly
* Explicitly specify types of integer and floating point literals
* Add more test cases (mostly inspired by divtf3_test.c)
  - tests are added for obviously special cases such as +/-Inf, +/-0.0 and some
    more implementation-specific cases such as divisor being almost 1.0
* Make NaN in the second test case of `divtf3` to be `sNaN` instead of
  testing for `qNaN` again

Reviewed By: sepavloff

Differential Revision: https://reviews.llvm.org/D84932