Populate CHANGELOG.md & update maven metadata

[karthick-rn]

Description

Update CHANGELOG.md to prepare for the beta package release. Also, addressed a valid bot comment from apiview on the name pattern.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, [see this page](https://github.com/Azure/azure-powershell/blob/master/documentation/development-docs/cleanin g-up-commits.md).

Testing Guidelines

• Pull request includes test coverage for the included changes.
  Note: No test changes required. This PR only updates Maven metadata (pom.xml) and documentation (CHANGELOG.md).

[Copilot]

Pull request overview

This PR prepares the azure-analytics-planetarycomputer data plane library for its initial 1.0.0-beta.1 release by populating the CHANGELOG with meaningful release notes and correcting the Maven <name> pattern to align with SDK naming conventions (as flagged by APIView).

Changes:

• Updated <name> in pom.xml from "Microsoft Azure SDK for PlanetaryComputer" to the correct "Microsoft Azure client library for PlanetaryComputer" pattern, and added the article "the" to the <description>.
• Replaced placeholder CHANGELOG headings with actual release notes covering the four client pairs (StacClient, DataClient, IngestionClient, SharedAccessSignatureClient), authentication, and LRO support.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pom.xml	Corrects <name> to the standard "Microsoft Azure client library for …" pattern; minor <description> grammar fix
CHANGELOG.md	Replaces empty section placeholders with descriptive beta.1 release notes

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

com.azure:azure-analytics-planetarycomputer