Render Arrow record batches progressively

[e-kotov]

Arrow.tableFromIPC(response) waits for the complete HTTP response before exposing any record batches, so smaller server-side batches currently create more layers without showing pixels earlier.

This change reads Arrow IPC with RecordBatchReader.from(response.body) and appends one stable Deck.gl layer as each batch arrives. The shared loader keeps the current parse2ArrowTable() path for GeoParquet and FlatGeobuf, including the new upstream FlatGeobuf support.

Verification

• node tests-js/progressive-arrow-batches.test.mjs
• JavaScript syntax checks for every file in inst/htmlwidgets/
• R CMD build .
• R CMD check --no-manual deckglgeoarrow_0.1.0.9001.tar.gz

The JavaScript regression test verifies that the first layer is installed before the second Arrow batch is read and that the non-Arrow parser path remains available. The package check completes with the warnings already present on current main for the removed point-cloud methods and the development geoarrowWidget FlatGeobuf helper.

[e-kotov]

@tim-salabim this is in relation to the batching question, but ignore for now