This is useful where tests previously encoded information in the name
names of ranges and points. Currently, this is pretty limited because
names consist of only alphanumeric characters and '_'.
With this patch, we can keep the names simple and attach optional
payloads to ranges and points instead.
The new syntax should be fully backwards compatible (if I haven't missed
anything). I tested this against clangd unit tests and everything still passes.
Differential Revision: https://reviews.llvm.org/D137909
3cf14a7bdc