[acrcssc] Un-pin the cssc image version to let the latest cached image be picked by acr task infra automatically during task runs

[Ruchii-27]

PR Description:

• As of today, each cssc image update requires modifying the pinned image tag in the task definitions and releasing a new CLI extension version. By unpinning the version, patch updates to the cssc image can be rolled out independently without a CLI release cycle.
• This also ensures the cached version of the cssc image is always used, resulting in faster task runs since the task infrastructure doesn't need to pull a specific (potentially uncached) image tag.

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[azure-client-tools-bot-prd]

️✔️Azure CLI Extensions Breaking Change Test

️✔️Non Breaking Changes

[yonzhan]

Thank you for your contribution! We will review the pull request and get back to you soon.

[github-actions]

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[github-actions]

• For more info about extension versioning, please refer to Extension version schema

[Copilot]

Pull request overview

This PR updates the acrcssc Azure CLI extension to stop pinning a specific CSSC container image tag in the ACR Task YAML templates, so task runs can use the task infrastructure’s cached/latest CSSC image without requiring an extension release for each image patch.

Changes:

• Bump extension version to 1.0.0b7 and add release notes.
• Remove the pinned mcr.microsoft.com/acr/cssc:<tag> reference from multiple ACR Task YAML templates (including the dry-run template).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/acrcssc/setup.py	Version bump to 1.0.0b7.
src/acrcssc/HISTORY.rst	Add changelog entry describing the unpin behavior.
src/acrcssc/azext_acrcssc/templates/tmp_dry_run_template.yaml	Remove pinned CSSC image reference from template values.
src/acrcssc/azext_acrcssc/templates/task/cssc_trigger_workflow.yaml	Remove pinned CSSC image reference from workflow trigger task template.
src/acrcssc/azext_acrcssc/templates/task/cssc_scan_image.yaml	Remove pinned CSSC image reference from scan task template.
src/acrcssc/azext_acrcssc/templates/task/cssc_patch_image.yaml	Remove pinned CSSC image reference from patch task template.

[cegraybl]

LGTM