Add ktlint-configuration-report task to report ktlint configurations

[JLLeitschuh]

We get quite a few issues that are maybe rooted in ktlint, and maybe roote in ktlint-gradle. Adding a reporting task that communicates information like "this is what we sent to ktlint" and "this is what ktlint interpreted that to mean", would help with debugging these issues and hopefully give end-users the tools to figure out problems themselves instead of asking us.

Related:

• Expose information about files/resources that will be accessed when invoking ktlint pinterest/ktlint#1446
• Add API for retrieving the list of files that will be accessed pinterest/ktlint#1659

Information ideally provided:

• Listing the .editorconfig file was actually resolved and is being used
• What setting has ktlint actually read from that .editorconfig file
• A summary of the paths the .editorconfig file was applied to