SI-7895 Avoid cascade of "symbol not found" in pattern matches

If we can't type check the `Foo` in `case Foo(a, b) => (a, b)`,
we should enter error symbols for `a` and `b` to avoid further
errors being reported in the case body.
SI-7895 Issue all buffered errors after silent mode.

Rather than just the first.

For example, `foo(wizzle, wuzzle, woggle)` should report all three
not-found symbols.
SI-7985 Typecheck args after failure to typecheck function

`missing1.foo(missing2)` now reports `missing1` and `missing2` as
not found. Previously, only the first was reported.