ARROW-18337: [R] Possible undesirable handling of POSIXlt objects

[paleolimbot]

Before this PR, an attempt to print an ExtensionScalar would segfault:

> arrow::Scalar$create(arrow::vctrs_extension_array(4))
Scalar
/Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/result.cc:28: ValueOrDie called on an error: NotImplemented: construction from scalar of type numeric(0)
/Users/deweydunnington/Desktop/rscratch/arrow/cpp/src/arrow/array/util.cc:545  VisitTypeInline(*scalar_.type, this)
0   libarrow.1100.0.0.dylib             0x000000014d61dbec _ZN5arrow4util7CerrLog14PrintBackTraceEv + 52
1   libarrow.1100.0.0.dylib             0x000000014d61db68 _ZN5arrow4util7CerrLogD2Ev + 116
2   libarrow.1100.0.0.dylib             0x000000014d61dab4 _ZN5arrow4util7CerrLogD1Ev + 28
3   libarrow.1100.0.0.dylib             0x000000014d61dae0 _ZN5arrow4util7CerrLogD0Ev + 28
4   libarrow.1100.0.0.dylib             0x000000014d61d9a8 _ZN5arrow4util8ArrowLogD2Ev + 96
5   libarrow.1100.0.0.dylib             0x000000014d61d9ec _ZN5arrow4util8ArrowLogD1Ev + 28
6   libarrow.1100.0.0.dylib             0x000000014d30d888 _ZN5arrow8internal14DieWithMessageERKNSt3__112basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE + 68
7   libarrow.1100.0.0.dylib             0x000000014d30d900 _ZN5arrow8internal17InvalidValueOrDieERKNS_6StatusE + 76
8   libparquet.1100.0.0.dylib           0x000000010bb250d0 _ZNO5arrow6ResultINSt3__110shared_ptrINS_5ArrayEEEE10ValueOrDieEv + 52
9   libarrow.1100.0.0.dylib             0x000000014d313ff0 _ZNO5arrow6ResultINSt3__110shared_ptrINS_5ArrayEEEEdeEv + 40
10  libarrow.1100.0.0.dylib             0x000000014d313880 _ZNK5arrow6Scalar8ToStringEv + 692
11  arrow.so                            0x0000000103c54fec _arrow_Scalar__ToString + 108

After this PR, we get the result of format(ext_scalar$as_vector()):

arrow::Scalar$create(arrow::vctrs_extension_array(4))
#> Scalar
#> 4

This came up because the some relatively common (ish) R type POSIXlt is now transformed to an extension array by default:

arrow::Scalar$create(as.POSIXlt(Sys.time()))
#> Scalar
#> 2023-01-09 14:55:53

[github-actions]

https://issues.apache.org/jira/browse/ARROW-18337

[github-actions]

⚠️ Ticket has not been started in JIRA, please click 'Start Progress'.

[thisisnic]

Excellent, cheers!

[ursabot]

Benchmark runs are scheduled for baseline = 157062d and contender = 92b5178. 92b5178 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Finished ⬇️1.08% ⬆️0.0%] test-mac-arm
[Finished ⬇️0.0% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.19% ⬆️0.09%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] 92b5178e ec2-t3-xlarge-us-east-2
[Finished] 92b5178e test-mac-arm
[Finished] 92b5178e ursa-i9-9960x
[Finished] 92b5178e ursa-thinkcentre-m75q
[Finished] 157062d4 ec2-t3-xlarge-us-east-2
[Finished] 157062d4 test-mac-arm
[Finished] 157062d4 ursa-i9-9960x
[Finished] 157062d4 ursa-thinkcentre-m75q
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java