Rename task::yield() to task::deschedule().

Fixes #8494.

Mostly optimizing TLS accesses to bring local heap allocation performance
closer to that of oldsched. It's not completely at parity but removing the
branches involved in supporting oldsched and optimizing pthread_get/setspecific
to instead use our dedicated TCB slot will probably make up for it.

this has been replaced by `for`

Change the former repetition::

    for 5.times { }

to::

    do 5.times { }

.times() cannot be broken with `break` or `return` anymore; for those
cases, use a numerical range loop instead.

To be more specific:

`UPPERCASETYPE` was changed to `UppercaseType`
`type_new` was changed to `Type::new`
`type_function(value)` was changed to `value.method()`

I removed the `static-method-test.rs` test because it was heavily based
on `BaseIter` and there are plenty of other more complex uses of static
methods anyway.

This only changes the directory names; it does not change the "real"
metadata names.

fail!() used to require owned strings but can handle static strings
now. Also, it can pass its arguments to fmt!() on its own, no need for
the caller to call fmt!() itself.