Migrate SkTLazy usage to std::optional

- eventually delete SkTLazy

A.set(B)    --> A = B
A.init(...) --> A.emplace(...)
A.get()     --> &A.value()
A.isValid() --> A.has_value()

A.getMaybeNull() --> SkOptAddressOrNull(A)

Change-Id: I07e14f40ccb8e01db9070c72a637ac1099e68cd5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1052677
Reviewed-by: Kaylee Lubick <kjlubick@google.com>
Reviewed-by: Daniel Dilan <danieldilan@google.com>
Commit-Queue: Mike Reed <mike@reedtribe.org>
18 files changed