Move a test from pos to run to highlight bytecode deficiencies.

We'll address them in subsequent commits.
SI-6666 Account for nesting in setting INCONSTRUCTOR

This flag is calcualed in Namers, and assigned to class
and module class symbols that are defined in self/super-calls,
and in early definitions.

For example, class D is INCONSTRUCTOR in each case below:

    class C extends Super({class D; ()})
    class C(a: Any) {
      def this(a: Any) = this({class D; ()})
    }
    new { val x = { class D; () } with Super(())

But, the calculation of this flag failed to account for
nesting, so it was not set in cases like:

    class C(a: Any) {
      def this(a: Any) = this({val x = {class D; ()}; x})
    }

This patch searches the enclosing context chain, rather than
just the immediate context. The search is terminated at the
first non term-owned context. In the following example, this
avoids marking `E` as INCONSTRUCTOR; only `D` should be.

    class C extends Super({class D { class E }; ()})

This closes SI-6259 and SI-6506, and fixes one problem
in the recently reopened SI-6957.
Add a test case from the comments of SI-6666.

This one lands in the new implementation restriction
which beats the VerifyError.