arrow

GH-27494: [R] Implement RPrimitiveConverter for Decimal type (#15211)

Implements conversion from R to Decimal128/256 in such a way that it works with `Array$create()`.

Before this PR:

``` r
library(arrow, warn.conflicts = FALSE)
#> Some features are not enabled in this build of Arrow. Run `arrow_info()` for more information.
Array$create(1)$cast(decimal(10, 2))
#> Array
#> <decimal128(10, 2)>
#> [
#>   1.00
#> ]

Array$create(1, type = decimal128(10, 2))
#> Error in `value[[3L]]()`:
#> ! NotImplemented: Extend
#> ℹ You might want to try casting manually with `Array$create(...)$cast(...)`.

#> Backtrace:
#>     ▆
#>  1. └─Array$create(1, type = decimal128(10, 2))
#>  2.   └─base::tryCatch(...) at r/R/array.R:198:2
#>  3.     └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>  4.       └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  5.         └─value[[3L]](cond)
#>  6.           └─rlang::abort(...) at r/R/array.R:202:6
Array$create(1, type = decimal256(10, 2))
#> Error in `value[[3L]]()`:
#> ! NotImplemented: Extend
#> ℹ You might want to try casting manually with `Array$create(...)$cast(...)`.

#> Backtrace:
#>     ▆
#>  1. └─Array$create(1, type = decimal256(10, 2))
#>  2.   └─base::tryCatch(...) at r/R/array.R:198:2
#>  3.     └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>  4.       └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  5.         └─value[[3L]](cond)
#>  6.           └─rlang::abort(...) at r/R/array.R:202:6
```

<sup>Created on 2023-01-05 with [reprex v2.0.2](https://reprex.tidyverse.org)</sup>

After this PR:

``` r
library(arrow, warn.conflicts = FALSE)
#> Some features are not enabled in this build of Arrow. Run `arrow_info()` for more information.
Array$create(1)$cast(decimal(10, 2))
#> Array
#> <decimal128(10, 2)>
#> [
#>   1.00
#> ]

Array$create(1, type = decimal128(10, 2))
#> Array
#> <decimal128(10, 2)>
#> [
#>   1.00
#> ]
Array$create(1, type = decimal256(10, 2))
#> Array
#> <decimal256(10, 2)>
#> [
#>   1.00
#> ]
```

<sup>Created on 2023-01-05 with [reprex v2.0.2](https://reprex.tidyverse.org)</sup>

TODO: test!

Lead-authored-by: Dewey Dunnington <dewey@fishandwhistle.net>
Co-authored-by: Dewey Dunnington <dewey@voltrondata.com>
Co-authored-by: Nic Crane <thisisnic@gmail.com>
Co-authored-by: Weston Pace <weston.pace@gmail.com>
Signed-off-by: Dewey Dunnington <dewey@fishandwhistle.net>