Breaking change 40678 requires the constructors int.fromEnvironment and
String.fromEnvironment to get new default values for the named
parameter `defaultValue`. This CL changes usages of these constructors
such that they do not depend on the default value, such that it
becomes a non-breaking change for code in the SDK repo to perform the
change in sdk and in sdk_nnbd.
Change-Id: I82af0e1f92d6cd3618b65c0c50d754ae8c39eb0a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/140284
Reviewed-by: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>
Commit-Queue: Erik Ernst <eernst@google.com>
Alexander Aprelev