Enable JVM and Native IR transformations by default

[mvicsokolova]

Enabling JVM and Native IR transformations by default would allow us to reveal existing problems with atomicfu-compiler-plugin in a secure manner, while still having the option to revert to legacy transformations if needed.

This step serves as preparation before the complete removal of JVM legacy bytecode transformations (#338).

Currently, the list of issues in atomicfu-compiler-plugin, which should be addressed can be found here on YT: #kotlinx-atomicfu