feat(downloadSSURGO): add LAPPLY.FUN argument for parallel unzipping

[brownag]

Adds arguments LAPPLY.FUN and LAPPLY.FUN.ARGS to downloadSSURGO()

Closes #470

Using future.apply::future_lapply() with a 8-session future plan, the OCONUS example extracts 158 ZIP files in about 3-5 seconds on my GFE. This is a massive improvement over sequential approach where massive latency in I/O for a few different reasons is a major blocker.

library(soilDB)
library(future)

plan(multisession, workers = 8)

td <- "ssurgo"

AREASYMBOLS <- SDA_query(
  "SELECT areasymbol, saverest 
   FROM sacatalog
   WHERE SUBSTRING(areasymbol, 0, 3) IN ('PR', 'VI', 'HI', 'AK', 'PW', 'GU', 'AS', 'MP');"
)$areasymbol

downloadSSURGO(
  areasymbols = AREASYMBOLS,
  destdir = td,
  include_spatial = "mupolygon",
  include_tabular = c("mapunit", "muaggatt"),
  extract = FALSE, 
  overwrite = TRUE
) |> system.time()

downloadSSURGO(
  areasymbols = AREASYMBOLS,
  destdir = td,
  include_spatial = "mupolygon",
  include_tabular = c("mapunit", "muaggatt"),
  LAPPLY.FUN = future.apply::future_lapply,
  overwrite = TRUE
) |> system.time()

createSSURGO(
  "OCONUS.gpkg",
  exdir = td,
  overwrite = TRUE
) |> system.time()

DBI::dbListTables(con <- NASIS("OCONUS.gpkg"))

con2 <- DBI::dbConnect(duckdb::duckdb("OCONUS.duckdb"))

createSSURGO(
  conn = con2,
  exdir = td, 
  overwrite = TRUE
) |> system.time()

DBI::dbListTables(con2)
DBI::dbDisconnect(con)
DBI::dbDisconnect(con2)