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GH-36671: [Go] BinaryMemoTable optimize allocations of GetOrInsert (#36811)



### Rationale for this change

The hashing.MemoTable provides an interface with

    GetOrInsert(val interface{}) (idx int, existed bool, err error)

This can cause a costly allocation for binary dictionaries as is detailed in issue https://github.com/apache/arrow/issues/36671

If we expand the MemoTable interface to include:

   
    GetOrInsertBytes(val []byte) (idx int, existed bool, err error)

We can avoid the allocations at runtime to convert from `[]byte` to `interface{}`

### What changes are included in this PR?

No logic was changed with the BinaryMemoTable but instead the same API for `GetOrInsert` was copied to a type specific API of `GetOrInsertBytes`. 

The `BinaryDictionaryBuilder` now simple calls these bytes methods instead of the generic `interface{}` ones.

### Are these changes tested?

No additional tests were included as the current tests exercise this code. 

### Are there any user-facing changes?

* Closes: #36671

Authored-by: thorfour <me@thor-hansen.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>