[FEA] Remove support for Spark 3.1.x

[sameerz]

Is your feature request related to a problem? Please describe. Remove support for Spark 3.1, as it is more than two years old per https://spark.apache.org/news/ . It no longer receives community updates.

Describe the solution you'd like

1. Remove Spark 3.1.x shims
2. We should have removed documentation references to 3.1 support at this point. We need to scrub and reconfirm there are no mentions of Spark 3.1.x support.

Describe alternatives you've considered

Additional context

[pxLi]

From CICD perspective,

1. Pick a new default - Done (confirmed as 3.2.0)
2. changes to CICD setup based on the new default (still building 3.1.x shims) - Done (6/14)
3. developer help switch the default shim to a 3.2.x version (stop building 3.1.x shims)
4. remove all the 3.1.x code

In these steps it should not block any nightly pipelines.

[pxLi]

@sameerz We have done above step 2. feel free to ask some developers to help deal with the drop support work and switch 2408 defaults in spark-rapids and spark-rapids-private. @NvTimLiu will help with the test scripts during the process.

Also as @gerashegalov mentioned in https://github.com/NVIDIA/spark-rapids/issues/11061, it would be nice to re-consider a better way to do shims version management~

[NvTimLiu]

We still have some following up issues for this removing spark31x shims ticket, suppose dev team will help on them, thanks! cc @jlowe

https://github.com/NVIDIA/spark-rapids/issues/11160

https://github.com/NVIDIA/spark-rapids/issues/11178