Add first performance options

[phvalguima]

Some of the early conclusions I've found. These options will not use memory maps for files but rather allow "direct" access. The advantage: mysql has its own engines to cache data and does not need the kernel to manage file caches itself.

[codecov[bot]]

Codecov Report

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

Project coverage is 65.90%. Comparing base (6bcd952) to head (41f6ea0).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #400 +/- ## ======================================= Coverage 65.90% 65.90% ======================================= Files 17 17 Lines 3103 3103 Branches 411 411 ======================================= Hits 2045 2045 Misses 929 929 Partials 129 129 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[7annaba3l]

Looks good to me also. Let's make those the defaults and not allow them to be changed. We will review our auto-tuned in the next 24.10 cycle, hopefully.

[taurus-forever]

Hi,

JFYI, I have made 1 hour tests on localhost for default and proposed parameters (twice). Env: Laptop=>Multipass QEMU=>LXD. For the small numbers (like 6K qpt) the difference is not really visible:

I still believe we should go with new defaults based on the previous test results done by Pedro.

P.S. Ignore significant spikes/drops on the localhost test, it looks like some laptop background tasks. No issues notices on charm/qemu itself.