Replace allocator with freeing-bump allocator (#1656)

* Link substrate issue tracker in panic

* Replace allocator with freeing-bump allocator

* Revert me: Panic on double allocate/free

* Revert me: Add shallow benchmark for a first impression

* Revert "Revert me: Add shallow benchmark for a first impression"

This reverts commit 5f0d4df39395eb55c9ec2d6fe1ed992533475fec.

* Revert "Revert me: Panic on double allocate/free"

This reverts commit a114df7d6cfc21d60af396ccca02e5c8205db6ce.

* Rename heap to FreeingBumpHeapAllocator

* Rename heap.rs to allocator.rs

* Use sandbox heap

* Move functions

* Move variables into constructor

* Revert "Move variables into constructor"

This reverts commit f46fa0d0cdf4ea97760ccce58003b0d33f433743.

* Remove unnecessary casts

* Add comment for new parameter

* Improve typing

* Move variables into constructor

* Avoid dynamic allocation

* Remove unused variables

* Revert "Link substrate issue tracker in panic"

This reverts commit 32dfa1d02bcf881d1d514a930fcc0fdf3c5f8e08.

In the meantime this was fixed in https://github.com/paritytech/substrate/pull/1667.

* Improve naming

* Only assert in debug mode

* Remove dynamic allocation