eval PARAM_PATH argument on Docker buildx

[n2taylor]

Checklist

• [x] All new jobs, commands, executors, parameters have descriptions
• [x] Examples have been added for any significant new features
• [x] README has been updated, if necessary

Motivation, issues

Per my comment here, it would be great if we could pass a dynamic path name to build-and-push-image, in the case where we want to use it for multiple Docker builds within the same config (such as using the matrix: style jobs).

Description

Added an eval on the PARAM_PATH argument to buildx.

[stale[bot]]

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