KVListFormat shadow's the Key if It is not a valid string

[harshanarayana]

/kind bug

What steps did you take and what happened:
While trying to take a stab at #275 I noticed that there is a lingering issue in the KVListFormat function in terms of how it processes the keys

klog/internal/serialize/keyvalues.go

Lines 112 to 118 in 9c48b7d

	if k, ok := k.(string); ok {
	// Avoid one allocation when the key is a string, which
	// normally it should be.
	b.WriteString(k)
	} else {
	b.WriteString(fmt.Sprintf("%s", k))
	}

In case if the key passed to the KVListFormat is not of string type, this ends up consuming the key and only printing the value.

What did you expect to happen:
Based on the current comment/code, the expectation is that it will log the struct using fmt.Sprintf("%s", k) however, this is not working due to variable getting shadow'ed.

Anything else you would like to add:
NA

[harshanarayana]

/assign