The previous commit moved all test files from `std` to `core` so git
understands the move. Not all functionality is actually testable in
`core`, however, so perform move the relevant portions back. Changes
from inherent to module methods is also done since this is the form of
math operations available in `core` (as `core_float_math`).
Many float-related tests in `std` only depend on `core`, so move the
tests there. This also allows us to verify functions from
`core_float_math`.
Since the majority of test files need to be moved to `coretests`, move
the files here without any cleanup; this is done in a followup commit.
This makes git history slightly cleaner, but coretests will not build
immediately after this commit.
New compiler configuration has been introduced that is designed to
replace the build script configuration `reliable_f16`, `reliable_f128`,
`reliable_f16_math`, and `reliable_f128_math`. Do this replacement here,
which allows us to clean up `std`'s build script.
All tests are gated by `#[cfg(bootstrap)]` rather than doing a more
complicated `cfg(bootstrap)` / `cfg(not(bootstrap))` split since the
next beta split is within two weeks.
