Implements a chunking strategy for the element arena that allows it to
grow dynamically based on allocations, it is initialised with a single
chunk of a total size of 1 mebibyte. On allocation of data with a size
greater than the remaining space of the current chunk a new chunk is
created.

This reduces the memory allocation from the static 32 mebibytes, this
especially helps GPUI applications that don't need such a large element
arena and even Zed in most cases. This also prevents the panic when
allocations ever exceed the element arena.

Release Notes:

- N/A

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Co-authored-by: Michael Sloan <michael@zed.dev>