SQLite cache: Use `requests_cache.CachedSession` for better concurrency

[amotl]

About

• @JensRichnow recently reported problems with concurrency on fast / highly concurrent machines, like the Apple M2 Max.

  • GH-111

• @JWCook suggested to use requests_cache.CachedSession to improve the situation.

  • https://github.com/requests-cache/requests-cache/issues/870#issuecomment-1716370826
  • https://github.com/panodata/grafana-wtf/issues/111#issuecomment-1837550141

• This patch aims to do just that. Thank you very much!

Details

Users on Apple M2 Max reported DB lock errors:

[grafana_wtf.core]
  INFO: Fetching dashboards in parallel with 5 concurrent requests

[requests_cache.backends.sqlite]
  WARNING: Database is locked in thread 6272069632; retrying (1/3)

Also segmentation faults, and leaks:

  UserWarning: resource_tracker: There appear to be 1 leaked semaphore
  objects to clean up at shutdown

NB: @Ousret, @JWCook: Just in case you didn't know yet -- Apparently, using Niquests together with Requests-Cache works well, at least according to the succeeding test suite.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 86.68%. Comparing base (76e1abd) to head (5583ae0).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #130 +/- ## ========================================== + Coverage 86.50% 86.68% +0.17% ========================================== Files 8 9 +1 Lines 1060 1074 +14 ========================================== + Hits 917 931 +14 Misses 143 143 ``` | [Flag](https://app.codecov.io/gh/panodata/grafana-wtf/pull/130/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=panodata) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/panodata/grafana-wtf/pull/130/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=panodata) | `86.68% <100.00%> (+0.17%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=panodata#carryforward-flags-in-the-pull-request-comment) to find out more.

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