third_party/fuchsia: Pull in fit::function tests
third_party/fuchsia: Pull in fit::function tests

Sync function_tests.cc so Pigweed can run the fit::function tests in its
environment.

Change-Id: I920af7f8b88967fcd6620bd41d32e63a76d5d93b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/109716
Commit-Queue: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <cca3bedb37979eacd157a9bceb473582df8aea1e@google.com>
Reviewed-by: Rob Mohr <d07614a8a0b466db08f68224f87d738b0f9615cf@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed