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GH-33887: [Go] cdata package leaks handles, difficult debugging (#33889)



### Rationale for this change
Fixing a memory leak of malloc'd `uintptr_t` values used for cgo handles

### What changes are included in this PR?
calling `free` on the handles after deleting the Go objects they point at, add `static` keyword to the helper function definitions in `helpers.h` so that compiling without optimizations for debugging doesn't fail.

* Closes: #33887

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