Disallow inlining functions containing early returns.

This allows us to remove 100 LOC from the inliner and is very unlikely
to affect any existing benchmark. We don't have any evidence to support
the idea that a one-iteration `for` loop with `continue`-based exits
will be any faster than a standard function call on any existing GPU.
Our fragment processors are generally written to avoid early returns,
in large part to avoid hitting this path.

This drastically impacts BlendEnum.sksl (which can no longer flatten out
a switch over every blend function in SkSL) but is otherwise a wash.

See: http://go/optimization-in-sksl-inliner suggestion 4(a)

Change-Id: I1f9c27bcd7a8de46cc4e8d0b9768d75957cf1c50
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/385377
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
12 files changed