Add --properties-separator option (#1951)

This commit adds the --properties-separator option, which lets users
specify the separator used between keys and values in the properties
output format. This is done by adjusting the value of
github.com/magiconair/properties#Properties.WriteSeparator at encode
time.

Some refactoring of the properties encoder unit tests was done to make
it easier to write unit tests that include different separator values.

Fixes: #1864

Signed-off-by: Ryan Drew <ryan.drew@isovalent.com>

pkg/yqlib/encoder_properties.go

@@ -12,11 +12,13 @@ import (
 
 type propertiesEncoder struct {
 	unwrapScalar bool
+	prefs        PropertiesPreferences
 }
 
-func NewPropertiesEncoder(unwrapScalar bool) Encoder {
+func NewPropertiesEncoder(unwrapScalar bool, prefs PropertiesPreferences) Encoder {
 	return &propertiesEncoder{
 		unwrapScalar: unwrapScalar,
+		prefs:        prefs,
 	}
 }
 
@@ -69,6 +71,7 @@ func (pe *propertiesEncoder) Encode(writer io.Writer, node *CandidateNode) error
 
 	mapKeysToStrings(node)
 	p := properties.NewProperties()
+	p.WriteSeparator = pe.prefs.KeyValueSeparator
 	err := pe.doEncode(p, node, "", nil)
 	if err != nil {
 		return err