Slow query log should use System#nanoTime not System#currentTimeMillis

Description

Currently, the slow query log using `System#currentTimeMillis`, that is not suitable for calculating time durations, as stated by the Java Doc:

Note that while the unit of time of the return value is a millisecond, the granularity of the value depends on the underlying operating system and may be larger. For example, many operating systems measure time in units of tens of milliseconds.

We should use `nanoTime` instead.

Environment

None

Assignee

Vlad Mihalcea

Reporter

Vlad Mihalcea

Fix versions

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Priority

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