fix: ignore lazy definition generated from by-name implicits

[danielleontiev]

Preamble:

by-name implicit parameters used for shapeless magic and were introduced in SIP-31 (available from 2.13+):
https://docs.scala-lang.org/sips/byname-implicits.html

Using scoverage with such code may result in the following warning from the plugin:

[warn] Could not instrument [Select/value rec$1].

Originally discovered by using scoverage with the code that derives typeclass instances using kittens library:

case class Bar()
case class Foo(bars: List[Bar])
object Foo {
  implicit eq: cats.Eq[Foo] = cats.derived.semiauto.eq
}

Solution:

Ignore LazyDefns$1.rec$1 from instrumentation like other synthetic code

Other changes:

It was necessary to disable position validation phase for the test case that reproduces the issue because the code generated by scala compiler fails such validation. It could be also checked outside testing environment by manually setting -Yvalidate-pos:typer option to the compiler. Not sure whether it's expected compiler behavior or not

[ckipp01]

Thanks for this @danielleontiev! And thanks for the explanations. Regarding the position validation behavior, to be honest I'm not really sure what's happening there. However all tests are passing so I'm pretty comfortable merging.