std: Make ~[T] no longer a growable vector

This removes all resizability support for ~[T] vectors in preparation of DST.
The only growable vector remaining is Vec<T>. In summary, the following methods
from ~[T] and various functions were removed. Each method/function has an
equivalent on the Vec type in std::vec unless otherwise stated.

* slice::OwnedCloneableVector
* slice::OwnedEqVector
* slice::append
* slice::append_one
* slice::build (no replacement)
* slice::bytes::push_bytes
* slice::from_elem
* slice::from_fn
* slice::with_capacity
* ~[T].capacity()
* ~[T].clear()
* ~[T].dedup()
* ~[T].extend()
* ~[T].grow()
* ~[T].grow_fn()
* ~[T].grow_set()
* ~[T].insert()
* ~[T].pop()
* ~[T].push()
* ~[T].push_all()
* ~[T].push_all_move()
* ~[T].remove()
* ~[T].reserve()
* ~[T].reserve_additional()
* ~[T].reserve_exect()
* ~[T].retain()
* ~[T].set_len()
* ~[T].shift()
* ~[T].shrink_to_fit()
* ~[T].swap_remove()
* ~[T].truncate()
* ~[T].unshift()
* ~str.clear()
* ~str.set_len()
* ~str.truncate()

Note that no other API changes were made. Existing apis that took or returned
~[T] continue to do so.

[breaking-change]
Update the rest of the compiler with ~[T] changes
auto merge of #13588 : alexcrichton/rust/no-more-growing, r=thestinger

This is all in preparation for DST. This removes all the growable/shrinkable methods from `~[T]`.
Add git to README.md dependency list because configure requires it
auto merge of #13601 : mdinger/rust/readme, r=brson

Configure required git be installed so this should be added to the dependencies list.  If it's only required when using git, a note could also be added.