Merge #17125: gui: Add toolTip and placeholderText to sign message fields

610d938 gui: Added label & tooltip for Verify Message labels (dannmat)

Pull request description:

  When using the Verify Message functionality, I found the input boxes to be rather confusing as they had no guidance for their purpose.

  I have added tooltips and labels to aid users when verifying messages in future

ACKs for top commit:
  promag:
    Code review ACK 610d938. Nit, commit and title are a little weird. Suggestion: "gui: Add toolTip and placeholderText to sign message fields"
  MarcoFalke:
    ACK 610d938 (looks good, didn't compile or tested the changes)
  fanquake:
    ACK - 610d938

Tree-SHA512: d6a1bc872ad270dce440e96a163ce72cdd4708913d87a0fea749fc8cf2d8163b791cbb96a82030e0cb7d239920ceb0e3f05e0eec113f45a1a8e1309fbd92b4b0

Author: fanquake

src/qt/forms/signverifymessagedialog.ui

@@ -285,10 +285,24 @@
         </layout>
        </item>
        <item>
-        <widget class="QPlainTextEdit" name="messageIn_VM"/>
+        <widget class="QPlainTextEdit" name="messageIn_VM">
+          <property name="toolTip">
+            <string>The signed message to verify</string>
+          </property>
+          <property name="placeholderText">
+            <string>The signed message to verify</string>
+          </property>
+        </widget>
        </item>
        <item>
-        <widget class="QValidatedLineEdit" name="signatureIn_VM"/>
+        <widget class="QValidatedLineEdit" name="signatureIn_VM">
+          <property name="toolTip">
+            <string>The signature given when the message was signed</string>
+          </property>
+          <property name="placeholderText">
+            <string>The signature given when the message was signed</string>
+          </property>
+        </widget>
        </item>
        <item>
         <layout class="QHBoxLayout" name="horizontalLayout_2_VM">