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Instead of repeating the same list parsing pattern for parenthesized
of braced comma or semicolon-separated lists, introduce a single list
parsing function that can be parametrized and which takes a closure
to parse list elements.

This ensures the same error handling and recovery logic is used across
all lists and simplifies the code.

No semantic change.

Change-Id: Ia738d354d6c2e0c3d84a5f1c7269a6eb95685edc
Reviewed-on: https://go-review.googlesource.com/70492

Reviewed-by: Matthew Dempsky <mdempsky@google.com>