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GH-38281: [Go] Ensure CData imported arrays are freed on release (#38314)



### Rationale for this change
The usage of `SetFinalizer` means that it's not *guaranteed* that calling `Release()` on an imported Record or Array will actually free the memory during the lifetime of the process. Instead we can leverage a shared buffer count, atomic ref counting and a custom allocator to ensure proper and more timely memory releasing when importing from C Data interface.

### What changes are included in this PR?
* Some simplifications of code to use `unsafe.Slice` instead of the deprecated handling of `reflect.SliceHeader` to improve readability
* Updating tests using `mallocator.Mallocator` in order to easily allow testing to ensure that memory is being cleaned up and freed
* Fixing a series of memory leaks subsequently found by the previous change of using the `mallocator.Mallocator` to track the allocations used for testing arrays.

### Are these changes tested?
Yes, unit tests are updated and included.

* Closes: #38281

Authored-by: Matt Topol <zotthewizard@gmail.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>