Use resizeMutableByteArray# and shrinkMutableByteArray# to resize MutArray

[harendra-kumar]

Currently we implement realloc by allocating a new array and copying the old array into it.

[rnjtranjan]

As per docs it works for unpinned mutable byte array only. In our code it works for pinned and unpinned both.

[harendra-kumar]

We already reuse the old array when we truncate up to a certain threshold, so we can continue using the existing code.