Change `log.Wrapper.UnmarshalText` to use `ErrorWithSentryWrapper` as the default one about baseplate.go

[fishy]

even if we changed the default of UnmarshalText to sentry, it won't help when the config line is not present in the yaml.
for example, say we have this config struct:

type Config struct {
  Logger log.Wrapper `yaml:"logger"`
  OtherThing int `yaml:"otherThing"`
  ...
}

for this yaml it works that we parse it as sentry:

logger:
otherThing: 3

for this yaml it doesn't work (the log.Wrapper will be nil):

otherThing: 3

so we need to change log.Wrapper's default to sentry as well.