remove no-std-compat

[Luro02]

This PR removes the dependency on the no-std-compat crate to make this crate have zero dependencies.

There is little benefit in using the crate, because as can be seen in the diff of the PR, there are only a few lines that have to be changed to make it work without it.

On my local machine the tests failed on nightly with confusing errors like this one:

error: #[quickcheck] is only supported on statics and functions
    --> src/tests.rs:1162:9
     |
1162 |         fn reordering_compact(insertions: u16, to_delete: Vec<u16>) -> bool {
     |         ^^
...
1238 |     gen_tests_for!(InlineStableVec);
     |     -------------------------------- in this macro invocation

idk why they fail, but they work on stable.