Check we can load duckdb extensions in a separate process

[dfalbel]

DuckDB extensions are shared libraries downloaded when
running INSTAll <name>. They are pre-built by the DuckDB
team https://github.com/duckdb/extension-ci-tools

They are built for the major platforms using the standard
compilers.

One of the CRAN test server is a Linux machine with R compiled
with clang instead of GCC. Since the compilers have different
ABIs, a crash happens when trying to execute extensions that are
pre-built on GCC.

To avoid the crash on CRAN machines, we check if the extensions can
be loaded in a separate process and proceed if that's possible. This follows the same pattern that's used by duckplyr in tidyverse/duckplyr#620

For reference this is how the crash looks on CRAN machines:

 *** caught segfault ***
address 0x6575716170, cause 'memory not mapped'

Traceback:
 1: rapi_execute(stmt, convert_opts)
 2: withCallingHandlers(expr, condition = function(cnd) {    {        .__handler_frame__. <- TRUE        .__setup_frame__. <- frame        if (inherits(cnd, "message")) {            except <- c("warning", "error")        }        else if (inherits(cnd, "warning")) {            except <- "error"        }        else {            except <- ""        }    }    while (!is_null(cnd)) {        if (inherits(cnd, "error")) {            out <- handlers[[1L]](cnd)            if (!inherits(out, "rlang_zap"))                 throw(out)        }        inherit <- .subset2(.subset2(cnd, "rlang"), "inherit")        if (is_false(inherit)) {            return()        }        cnd <- .subset2(cnd, "parent")    }})
 3: doTryCatch(return(expr), name, parentenv, handler)
 4: tryCatchOne(expr, names, parentenv, handlers[[1L]])
 5: tryCatchList(expr, classes, parentenv, handlers)
 6: tryCatch(withCallingHandlers(expr, condition = function(cnd) {    {        .__handler_frame__. <- TRUE        .__setup_frame__. <- frame        if (inherits(cnd, "message")) {            except <- c("warning", "error")        }        else if (inherits(cnd, "warning")) {            except <- "error"        }        else {            except <- ""        }    }    while (!is_null(cnd)) {        if (inherits(cnd, "error")) {            out <- handlers[[1L]](cnd)            if (!inherits(out, "rlang_zap"))                 throw(out)        }        inherit <- .subset2(.subset2(cnd, "rlang"), "inherit")        if (is_false(inherit)) {            return()        }        cnd <- .subset2(cnd, "parent")    }}), stackOverflowError = handlers[[1L]])
 7: rlang::try_fetch(rapi_execute(stmt, convert_opts), error = function(e) {    rethrow_error_from_rapi(e, call)})
 8: rethrow_rapi_execute(res@stmt_lst$ref, duckdb_convert_opts_impl(res@connection@convert_opts,     arrow = res@arrow))
 9: duckdb_execute(res)
10: duckdb_result(connection = conn, stmt_lst = stmt_lst, arrow = arrow)
11: .local(conn, statement, ...)
12: dbSendQuery(conn, statement, ...)
13: dbSendQuery(conn, statement, ...)
14: dbSendStatement(conn, statement, ...)
15: dbSendStatement(conn, statement, ...)
16: dbExecute(con, "INSTALL fts; LOAD fts;")
17: dbExecute(con, "INSTALL fts; LOAD fts;")
18: ragnar_store_build_index_v2(store, type)
19: ragnar_store_build_index(store)
An irrecoverable exception occurred. R is aborting now ...

[t-kalinowski]

Can you please add NEWS?