funcr: Fix bug in repeated calls to WithValues

[thockin]

When using RenderValuesHook we need to save the raw value, not the
rendered form.

Fixes #120

@pohly let's not sit on it too long - we can tag a 1.2.1 maybe next week?

@DazWilkin FYI

[DazWilkin]

Thank you!

Will try this tomorrow.

[DazWilkin]

Works for me! Thank you.

Revert to the naive renderLabels:

func(kvList []interface{}) []interface{} {
  return []interface{}{loggingLabels, funcr.PseudoStruct(kvList)}
}

Bumped go-logr to github.com/go-logr/logr v1.2.1-0.20211125105631-eeeb6242dad5

Code effectively:

j := NewStructuredLogger()
j = j.WithValues("foo", "X")
j = j.WithValues("bar", "Y")

Deployed to Cloud Run (one of the services that supports structured logging):

jsonPayload:
  level: 0
  logger: structured-logging
  msg: test
  ts: '2021-11-30 17:34:36.639675'
labels: # <--- CORRECT
  bar: Y
  foo: X
sourceLocation:
  file: main.go
  function: main.main
  line: '127'

[thockin]

Thanks for the confirmation