Improve `LICENSE` and `NOTICE` checks for binary packages

[sbp]

Our release policy says:

For source packages, LICENSE and NOTICE MUST be located at the root of the distribution. For additional packages, they MUST be located in the distribution format's customary location for licensing materials, such as the META-INF directory of Java "jar" files.

But currently we are checking for LICENSE and NOTICE files in binaries in the root. This was a problem during an Apache Maven Daemon release, and prevented them from using ATR because this is a blocking check. We can gradually add package format specific license and notice file path checks, but for now we should remove this check as it is unreliable, does not confirm to policy, and prevents releases.

[sbp]

Additionally, we will allow LICENSE.txt and NOTICE.txt in source files.

[dave2wave]

No. We'll discuss soon.

[sbp]

We're going to do a recursive search for them.

[sbp]

We're going to do a recursive search for them in binaries.

[sbp]

We're going to do a recursive search for them in binaries.