[r] Remove TileDB-R accesses within tests/testthat

[johnkerl]

grep tiledb:: tests/testthat | cat -n shows over 200 spots which are relying on tiledb-r for various assertions. These need to be worked off.

Inventory:

tests/testthat/test-SOMASparseNDArray.R     68
tests/testthat/test-SOMADataFrame.R         68
tests/testthat/test-SOMADenseNDArray.R      57
tests/testthat/test-Arrow-utils.R           14
tests/testthat/helper-test-soma-objects.R   6
tests/testthat/helper-test-tiledb-objects.R 5
tests/testthat/test-TileDBGroup.R           2
tests/testthat/test-SOMATileDBContext.R     2
tests/testthat/test-OrderedAndFactor.R      2
tests/testthat/test-example-datasets.R      1
tests/testthat/test-TileDBArray.R           1
tests/testthat/test-SOMAExperiment-query.R  1
tests/testthat/test-SOMACollection.R        1

Categorizing:

• A few of these are is-array or is-group checks which can be just as easily done using tiledbsoma-r
• The massive line-counts of occurrences of tiledb:: on test-SOMASparseNDArray.R, test-SOMADenseNDArray.R, and test-SOMADataFrame.R are due mainly to using tiledb-r to introspect on compression filters etc. that we written using tiledbsoma-r and platform_config but for which we lack a way to read back and verify in tiledbsoma-r -- or tiledbsoma-py for that matter -- please see https://github.com/single-cell-data/TileDB-SOMA/pull/3129/files#r1787917405

Context: #2406

[sc-56845]