fix(pkg): display if any of multiple attributes exist (npm#7855)

<!-- What / Why -->
<!-- Describe the request in detail. What it does and why it's being
changed. -->

See npm#7854 for the why and more details.

I changed the unwrap logic so that it only runs when the result contains
one entry and the amount of arguments is one. Otherwise, when multiple
arguments are provided the unwrap results in an undefined. Additionally,
I think it makes sense to skip the unwrap logic when the result contains
one entry and pkg has multiple arguments because you would expect an
object.

In the existing comment above the if-statement, it is mentioned the CLI
should not unwrap at all. I chose not to do this because it is not clear
to me if this is a final decision and has a large impact. However, if it
is the desired direction, I am happy to do the work.

## References
Fixes npm#7854

lib/commands/pkg.js

@@ -63,12 +63,12 @@ class Pkg extends BaseCommand {
 
     if (args.length) {
       result = new Queryable(result).query(args)
-      // in case there's only a single result from the query
-      // just prints that one element to stdout
+      // in case there's only a single argument and a single result from the query
+      // just prints that one element to stdout.
       // TODO(BREAKING_CHANGE): much like other places where we unwrap single
       // item arrays this should go away. it makes the behavior unknown for users
       // who don't already know the shape of the data.
-      if (Object.keys(result).length === 1) {
+      if (Object.keys(result).length === 1 && args.length === 1) {
         result = result[args]
       }
     }

test/lib/commands/pkg.js

@@ -108,6 +108,26 @@ t.test('get multiple arg', async t => {
   )
 })
 
+t.test('get multiple arg with only one arg existing', async t => {
+  const { pkg, OUTPUT } = await mockNpm(t, {
+    prefixDir: {
+      'package.json': JSON.stringify({
+        name: 'foo',
+      }),
+    },
+  })
+
+  await pkg('get', 'name', 'version', 'dependencies')
+
+  t.strictSame(
+    JSON.parse(OUTPUT()),
+    {
+      name: 'foo',
+    },
+    'should print retrieved package.json field'
+  )
+})
+
 t.test('get multiple arg with empty value', async t => {
   const { pkg, OUTPUT } = await mockNpm(t, {
     prefixDir: {