ci: add Docker layer caching to speed up builds

[robertodauria]

Summary

• Pull the latest image before building to use as a cache source
• Add --cache-from flag to reuse Docker layers from previous builds
• Speeds up subsequent builds when Dockerfile layers haven't changed

[coveralls]

Pull Request Test Coverage Report for Build 21221552674

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 21220919018:	0.0%
Covered Lines:	0
Relevant Lines:	104

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💛 - Coveralls