Replace viper with koanf in builder (open-telemetry#4757)

* replace viper with koanf in builder

Signed-off-by: Ryan Leung <rleungx@gmail.com>

* resolve the conflicts

Signed-off-by: Ryan Leung <rleungx@gmail.com>

* Update go.sum

Co-authored-by: Bogdan Drutu <bogdandrutu@gmail.com>
Co-authored-by: Bogdan Drutu <lazy@splunk.com>

cmd/builder/go.mod

@@ -17,31 +17,24 @@ module go.opentelemetry.io/collector/cmd/builder
 go 1.17
 
 require (
+	github.com/knadh/koanf v1.4.0
 	github.com/spf13/cobra v1.3.0
-	github.com/spf13/viper v1.10.1
 	github.com/stretchr/testify v1.7.0
 	go.uber.org/zap v1.21.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.5.1 // indirect
-	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
-	github.com/magiconair/properties v1.8.5 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/mapstructure v1.4.3 // indirect
-	github.com/pelletier/go-toml v1.9.4 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/spf13/afero v1.6.0 // indirect
-	github.com/spf13/cast v1.4.1 // indirect
-	github.com/spf13/jwalterweatherman v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
-	github.com/subosito/gotenv v1.2.0 // indirect
 	go.uber.org/atomic v1.7.0 // indirect
 	go.uber.org/multierr v1.6.0 // indirect
 	golang.org/x/sys v0.0.0-20211210111614-af8b64212486 // indirect
-	golang.org/x/text v0.3.7 // indirect
-	gopkg.in/ini.v1 v1.66.2 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )