Slow query log

[mamcx]

Description of Changes

Closes #1071

Log as tracing::warn! a query if it exceeds the threshold.

Note: Currently the default is burned here.

Note: The settings are not persited neither are transactional.

Is possible to query and set it at runtime:

🪐quickstart>SHOW slow_query_threshold;
 slow_query_threshold
----------------------
 100
 (1 row)
Time: 12.11ms

🪐quickstart>SET slow_query_threshold = 1
Time: 6.59ms
OK

The current settings:

slow_query_threshold = 100 ms
slow_incremental_updates_threshold = None
slow_subscriptions_threshold = None

Expected complexity level and risk

1

Testing

Describe any testing you've done, and any testing you'd like your reviewers to do,
so that you're confident that all the changes work as expected!

• test_slow_queries
• test_runtime_config
• Check with the sql cli that SET slow_query_threshold TO 1 and running a query print the warning

Don't have a way to check for stdout.

[mamcx]

Need to confirm which values will be nice for bitcraft and how to read them.

[joshua-spacetime]

This looks great @mamcx! Just a few more asks, but it should be ready to merge after that.

[joshua-spacetime]

Final naming suggestion :)

Suggested change

	ReadConfigOption::SlowQueryThreshold => "slow_ad_hoc_query_threshold",
	ReadConfigOption::SlowIncrementalUpdatesThreshold => "slow_incremental_query_threshold",
	ReadConfigOption::SlowSubscriptionsThreshold => "slow_subscription_query_threshold",
	ReadConfigOption::SlowQueryThreshold => "slow_ad_hoc_query_ms",
	ReadConfigOption::SlowIncrementalUpdatesThreshold => "slow_tx_update_ms",
	ReadConfigOption::SlowSubscriptionsThreshold => "slow_subscription_query_ms",

[Centril]

This seems to have regressed incr-select compared to HEAD~1 but the other benchmarks are unaffected.
On i7-7700K, 64GB RAM:

Benchmarking incr-select: Collecting 100 samples in estimated 5.0
incr-select             time:   [226.69 ns 228.30 ns 230.24 ns]
                        change: [+24.989% +26.097% +27.045%] (p = 0.00 < 0.05)
                        Performance has regressed.

[Centril]

Partially resolved by #1110.