indents(go): improve @branch rules

- Don't branch at `case`
- Let `import_spec_list`/`var_declaration` behave like
  `const_declaration`

Fixes #2166

tests/indent/go/multiple-vars.go

@@ -0,0 +1,19 @@
+package main
+
+var (
+	thing    = 1
+	thingTwo = 2
+) // <-- This paren should be at 0 instead of indented
+
+var (
+	thing    = 1
+	thingTwo = 2
+)
+
+func main() {
+	// It should be
+	var (
+		thing    = 1
+		thingTwo = 2
+	)
+}

tests/indent/go/switch.go

@@ -0,0 +1,14 @@
+// issue #2166
+package main
+
+import (
+	"fmt"
+)
+
+func test(ch byte) {
+	fmt.Println("hey!")
+	switch ch {
+	case 'l':
+		return
+	}
+}