refactor(system-tests): move dep-installer to own dir

[flotwig]

• For UNIFY-1036

User facing changelog

n/a

Additional details

• Cleanly move dependency installation code to it's own dir, in prep for test(system-tests): support npm for test projects #20664

How has the user experience changed?

n/a

PR Tasks

• [na[ Have tests been added/updated?
• [na] Has the original issue (or this PR, if no issue exists) been tagged with a release in ZenHub? (user-facing changes only)
• [na] Has a PR for user-facing changes been opened in cypress-documentation?
• [na] Have API changes been updated in the type definitions?
• [na] Have new configuration options been added to the cypress.schema.json?

[cypress-bot]

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[cypress]

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Test summary

19339 • 0 • 218 • 0 • 2

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Run details

Project	cypress
Status	Passed
Commit	360d8b7
Started	Mar 17, 2022 9:52 PM
Ended	Mar 17, 2022 10:03 PM
Duration	11:39 💡
OS	Linux Debian - 10.10
Browser	Multiple

View run in Cypress Dashboard ➡️

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Flakiness

	cypress/integration/reporter.hooks.spec.js		2
1	hooks > can rerun without timeout error leaking into next run (due to run restart)
2	hooks > can rerun without timeout error leaking into next run (due to run restart)

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