out_logrotate: add multiple log format tests and enhance multithreading support

This commit introduces several new test functions for various log formats including CSV, LTSV, plain text, MsgPack, and template formats. Additionally, it enhances the multithreading capabilities of the logrotate tests, ensuring that data is correctly handled and written in a concurrent environment. The changes also include helper functions for reading file content and verifying the output format.

Signed-off-by: SagiROosto <[email protected]>

Author: SagiROosto