ci(v2): improve usage of github actions cache

[galargh]

• Because this PR includes a bug fix, relevant tests have been included.
• Because this PR includes a new feature, the change was previously discussed on an Issue or with someone from the team.
• I didn't do anything of this.

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This PR is analogical to #5563 but it targets the main branch (and v2 packages) instead of v-next. See the full description in #5563

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Name	Status	Preview	Comments	Updated (UTC)
hardhat	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Aug 2, 2024 11:37am

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