Allow flexible constructor bodies

[findepi]

Java 25 adds ability to place statements within constructor before call to super(). Checkstyle does not support this yet, so it's configured not to fail the build on these.

[electrum]

This means we don't get any style checks for these files. Is it so important to use this feature before checkstyle supports it?

[findepi]

This means we don't get any style checks for these files.

Correct

Is it so important to use this feature before checkstyle supports it?

If checkstyle adds support for this soon, it doesn't matter.
If checkstyle doesn't add support for this soon, do we want to be held back?

Checkstyle is advisory only anyway. The fact the code passes checkstyle doesn't unfortunately prove it won't change on Intellij's reformat, which is quite useful property to have.