PS: Add a testcase for the new read step.

Author: MathiasVP

powershell/ql/test/library-tests/dataflow/fields/test.expected

@@ -181,6 +181,7 @@ nodes
 | test.ps1:89:6:89:12 | b | semmle.label | b |
 subpaths
 testFailures
+| test.ps1:92:13:92:31 | # $ hasValueFlow=18 | Missing result: hasValueFlow=18 |
 #select
 | test.ps1:4:6:4:9 | f | test.ps1:3:8:3:17 | Call to source | test.ps1:4:6:4:9 | f | $@ | test.ps1:3:8:3:17 | Call to source | Call to source |
 | test.ps1:11:6:11:13 | ...[...] | test.ps1:10:12:10:21 | Call to source | test.ps1:11:6:11:13 | ...[...] | $@ | test.ps1:10:12:10:21 | Call to source | Call to source |

powershell/ql/test/library-tests/dataflow/fields/test.ps1

@@ -86,4 +86,8 @@ Sink $hash["b"] # clean
 $hash["a"] = 0
 Sink $hash["a"] # $ SPURIOUS: hasValueFlow=16
 $hash.b = Source "17"
-Sink $hash.b # $ hasValueFlow=17
+Sink $hash.b # $ hasValueFlow=17
+
+foreach($a in 1, 2, (Source "18"), 3) {
+    Sink $a # $ hasValueFlow=18
+}