[DOCS] Prepare for 1.8.1 RC2: release notes and release script updates

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• No:
  • this is a documentation update. The PR name follows the format [DOCS] my subject

What changes were proposed in this PR?

This pull request updates the documentation for the Sedona 1.8.1 release and improves the Maven build and release instructions.

Release notes and documentation:

• Added detailed release notes for Sedona 1.8.1 in release-notes.md, including highlights, new features, bug fixes, improvements, and documentation updates.

Maven command and build process improvements:

• Removed the -q (quiet) flag from Maven commands in publish.md to make build logs more visible and easier to debug. [1] [2]
• Split mvn clean install commands into separate clean and install steps for each Spark/Scala/Java combination, improving clarity and reliability in the build process. [1] [2] [3]

How was this patch tested?

Tested locally

Did this PR include necessary documentation updates?

• Yes, I have updated the documentation.