When the BreakpointEditDialog is not paused at the breakpoint location,
property completion substituted source-mapped variables with their
generated names and evaluated them in the global scope. Generated locals
like `a` then resolved to unrelated globals, and we suggested their
properties as if they belonged to the authored variable.

Without a call frame at the location there is nothing to evaluate local
variables in. Only offer the statically known variable names in that
case and skip property and Map key completion. This also removes the
location-based name substitution from evaluateExpression().

Argument hints keep their behavior from before Location support: They
evaluate the callee as typed.

R=alexrudenko@chromium.org
Fixed: 567484416
Change-Id: I55f882b1e42356881f142c95fb97a0f827d8de2f
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/8479933
Reviewed-by: Alex Rudenko <alexrudenko@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>