[FEATURE REQUEST] Update Polaris doc site with new getting started examples

### Is your feature request related to a problem? Please describe.

Context: https://github.com/apache/polaris/pull/295#issuecomment-2353450842

https://polaris.apache.org/docs/quickstart

Update with new "getting started guide" for both Trino & Spark

### Describe the solution you'd like

_No response_

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

Start with the Polaris quickstart page at https://polaris.apache.org/docs/quickstart and review the context in PR #295, especially the linked issue comment. Update the getting started guidance with examples for both Trino and Spark, then verify that the revised documentation is complete and renders correctly.

Written by the indexing model from the issue text.