Kotlin 1.5 support

[Bencodes]

This PR includes:

• Support for Kotlin 1.5.x API and language levels
• Compiles rules_kotlin using 1.5.10
• Updates validate_kotlinc_options to fail fast when the new IR Kotlinc compiler flags that are enabled by default in 1.5 are passed in.

[Bencodes]

We are testing this in our repository and will report back.

[Bencodes]

It would be great to get this merged first so that we can be sure that there are no compose related regressions #493

[Bencodes]

We encountered this in our repository while testing 1.5.x bazelbuild/bazel#13553

[nkoroste]

Another issue we found #549

[Bencodes]

Another issue we found #549

@alexjlockwood also ran into something similar in a few of our targets.

[jeffzoch]

@Bencodes is bazelbuild/bazel#13553 blocking?

[Bencodes]

@jeffzoch we found a way to work around that issue inside our codebase so probably not a blocker.

[nkoroste]

@Bencodes Can you please describe what you did for your workaround?

[Bencodes]

@nkoroste The workaround is documented in the bazel_issue_13553 repo that I created for the bug report Bencodes/bazel_issue_13553#1

[cgruber]

As an FYI, I want to merge this, but I'm going to do a thing where I extract a copy of the builder and set it up separately as a 1.4-specific builder, then merge this in. @restingbull and I realized we are going to have to start segmenting the tooling so that we handle different kotlin versions a bit differently (initially with a big fat dupe with minor tweaks, later refactored into smaller deltas). But I'll merge this in, I just need to yoink out the other, first. (and then I'll have some hassle, probably, messing with 3rd party deps. Sigh).

[Kernald]

@Bencodes this can probably be closed now that #577 has been merged?