Because of the use of reflection in fx.Annotate, the error
messages for provide tend to refer to the annotated function as
`"reflect".makeFuncStub` which is not helpful for debugging.

This change updates error messages that previously looked like:
```
Failed: cannot provide function "reflect".makeFuncStub (/usr/local/go/src/reflect/asm_arm64.s:12):
cannot provide *fx_test.Logger from [0].Field0: already provided by "reflect".makeFuncStub
(/usr/local/go/src/reflect/asm_arm64.s:12)
```

To looking like this:
```
Failed: cannot provide function "reflect".makeFuncStub (/usr/local/go/src/reflect/asm_amd64.s:12):
cannot provide *fx_test.Logger from [0].Field0: already provided by "go.uber.org/fx_test".TestAnnotate.func1
(/gocode/src/github.com/uber-go/fx/annotated_test.go:515)
```

WIP: Planning on making a future fix that gives a more
readable name to the first function which still is referred to
as "reflect".makeFuncStub after this change.

Co-authored-by: Moises Vega <moises.vega@gmail.com>

Co-authored-by: Moises Vega <moises.vega@gmail.com>

Co-authored-by: Moises Vega <moises.vega@gmail.com>

Co-authored-by: Moises Vega <moises.vega@gmail.com>