Improve performance of Tracer.invoke() function

[OresteSalerno-TomTom]

Improve performance of Tracer.invoke():

• ~70% improvement if there are no trace event consumers
• ~55% improvement if there are trace event consumers

Changes:

• Introduce caching of trace event method annotations in the Tracer.invoke() function.
• Skip creation of a TraceEvent object if there are no event consumers. This saves us from performing an expensive LocalDateTime.now() call.
• Skip retrieval of trace event method annotations for simple log function invocations, if there are no event consumers.
• Remove string concatenations in createLogMessage() functions. Only use StringBuilder functions.
• Change toStringRegistry to use item::javaClass.name as key, and use item::class.toString() only as fallback.
• Skip reading item.javaClass.getMethod("toString").declaringClass in convertToStringUsingRegistry(): the item.toString() function of Any will anyway print the name of the class.
• Fix execution of unit tests requiring mockk-jvm (extensions and traceevents modules): no unit test for these modules was being run anymore, after the 1.8.2 update.
• Fix the IfExtensionsTest unit tests: these tests were broken by mockk 1.13.4 (due to Broken spying on functions mockk/mockk#1033).

[OresteSalerno-TomTom]

One note about the changes to the flow of the invoke() function: I have already tried a more elegant solution involving the use of lazy variables, but that had a worse performance impact than this solution. Instantiation of Lazy objects is not free.