ARROW-17458: [C++] Cast between decimal and string

[quanghgx]

[github-actions[bot]]

https://issues.apache.org/jira/browse/ARROW-17458

[github-actions[bot]]

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

[quanghgx]

Hi @westonpace This PR is ready for review. It relates to both ARROW-17042 and ARROW-17458

For 2 failed CI checks, it seems, they are not related to this change set: https://github.com/apache/arrow/actions/runs/3302286318/jobs/5448920608#step:6:2863 https://github.com/apache/arrow/actions/runs/3302286320/jobs/5448920508#step:7:7533

Sincerely,

[ursabot]

Benchmark runs are scheduled for baseline = b87370d6071cdb9313430e14482cbc4f7ad05e35 and contender = e9f0b3f7a33d5a992bc93a4ec2f3aa53a002ec75. e9f0b3f7a33d5a992bc93a4ec2f3aa53a002ec75 is a master commit associated with this PR. Results will be available as each benchmark for each run completes. Conbench compare runs links: [Finished :arrow_down:0.0% :arrow_up:0.0%] ec2-t3-xlarge-us-east-2 [Failed :arrow_down:0.0% :arrow_up:0.0%] test-mac-arm [Finished :arrow_down:0.27% :arrow_up:0.0%] ursa-i9-9960x [Failed :arrow_down:0.04% :arrow_up:0.0%] ursa-thinkcentre-m75q Buildkite builds: [Finished] e9f0b3f7 ec2-t3-xlarge-us-east-2 [Failed] e9f0b3f7 test-mac-arm [Finished] e9f0b3f7 ursa-i9-9960x [Failed] e9f0b3f7 ursa-thinkcentre-m75q [Finished] b87370d6 ec2-t3-xlarge-us-east-2 [Failed] b87370d6 test-mac-arm [Finished] b87370d6 ursa-i9-9960x [Finished] b87370d6 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