CCM-13478: Improve Pipeline Times

[ScottFullerton-NHSE]

Description

• Made the docs-build conditional.
• Integration tests set to run in parallel.
• npm dependency caching
• python pip caching
• Ruby bundling caching
• Removed test-coverage step as it wasn't used/required.

Context

Speeds up build pipelines which will save developers time when deploying/testing changes.

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming
• If I have used the 'skip-trivy-package' label I have done so responsibly and in the knowledge that this is being fixed as part of a separate ticket/PR.

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Sensitive Information Declaration

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Evidence of passing pipeline: https://github.com/NHSDigital/nhs-notify-digital-letters/actions/runs/21437075657

[gareth-allan]

This is a really nice improvement in build times! Looking at the build pipeline with these changes though, I wonder if we need to run the static analysis step after the unit tests have completed? I don't see a reason why we would need to, and if we can do it in parallel I think we could shave off another ~1m30s.

[gareth-allan]

This is a really nice improvement in build times! Looking at the build pipeline with these changes though, I wonder if we need to run the static analysis step after the unit tests have completed? I don't see a reason why we would need to, and if we can do it in parallel I think we could shave off another ~1m30s.

For the record, we discussed this offline, and the static analysis of course includes test coverage information so does need to run after the unit test step.