vk_memory_manager: Misc changes

* Allocate memory in discrete exponentially increasing chunks until the
128 MiB threshold. Allocations larger thant that increase linearly by
256 MiB (depending on the required size). This allows to use small
allocations for small resources.

* Move memory maps to a RAII abstraction. To optimize for debugging
tools (like RenderDoc) users will map/unmap on usage. If this ever
becomes a noticeable overhead (from my profiling it doesn't) we can
transparently move to persistent memory maps without harming the API,
getting optimal performance for both gameplay and debugging.

* Improve messages on exceptional situations.

* Fix typos "requeriments" -> "requirements".

* Small style changes.