address compiler warnings/errors and setup kind-projector migration

Some source files are moved or copy-pasted to reduce compile
errors in Scala 3.

They will be removed after tweaking build in future commits.

copy changes from twitter#1108 to make it easier to resolve conflict

use Math.random() to avoid auto application of `()` while keeping
compatibility between 2.11 and 2.13

scalameta says "pattern must be a value" for macro entrypoint, but it
compiles and is proper format.

 Workaround: skip compiling java api for Scala 3 because
 1. it seems Scala 3 generates Monoid$ in later stage than Scala 2.x,
    which prevents javaapi from compiling due to missing symbol.
 2. we cannot use `compileOrder := CompileOrder.ScalaThenJava`
    as algebird-core must compile CassandraMurmurHash.java BEFORE Scala,
    but at the same time algebird-core must compile javaapi AFTER Scala.