CI: Use `runner.arch` in cache keys along with `runner.os`

[bayandin]

Problem

Cache keys that we use on CI are the same for X64 and ARM64 (runner.arch)

Summary of changes

• Include runner.arch along with runner.os into cache keys

Checklist before requesting a review

• [x] I have performed a self-review of my code.
• [ ] If it is a core feature, I have added thorough tests.
• [ ] Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• [ ] If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• [ ] Do not forget to reformat commit message to not include the above checklist

[github-actions[bot]]

2934 tests run: 2817 passed, 0 failed, 117 skipped (full report)

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Flaky tests (1)

#### Postgres 14 - `test_location_conf_churn[3]`: [debug](https://neon-github-public-dev.s3.amazonaws.com/reports/pr-8175/9686364317/index.html#suites/231aea51ea102d83d3dae52232693454/8d47f4f23ff56ee/retries)

Code coverage* (full report)

• functions: 32.6% (6892 of 21116 functions)
• lines: 50.0% (53919 of 107861 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
5187d4b6d9cfe1c429baf0147b0578521d04e1ed at 2024-06-26T21:50:42.668Z :recycle:}