Revert "feat(compiler): support ScopeAware for decorators"

This reverts commit 9659dd1721c8011bd26d1855ca268a967805c4e2.

Wrong version of this PR was added in master, correct version is in
g3v1x.
feat(compiler): support ScopeAware for decorators

Even though decorators can safely inject scope (even after the proposed
context change), they might pick up ScopeAware from a base class shared
with components. Instead of manually calling super.scope = scope, we
support ScopeAware for decorators (similarly to Attach/DetachAware.)

There is no performance reduction on the tree benchmark.
chore(introspection): clean up workarounds for dart 1.4 and 1.5
fix(scope): fix a potential memory leak
perf(view): increase view instantiation speed 40%

1) Stop using futures when the value is already cached
2) Remove adding nodes to fake parent during view instantiation

Closes #1358