qml: add icon assets

Add SVG source files and PNG icons for the following:

- alert-filled: validation error indicator
- blockclock-icon: block clock display icon
- circle-file: snapshot file selection UI
- circle-green-check: snapshot loaded confirmation
- circle-red-cross: snapshot error state
- green-check: general success indicator
- pending-dark: dark theme pending indicator
- pending-light: light theme pending indicator

Update bitcoin_qml.qrc to register the new icon resources.

Author: johnny9

qml/bitcoin_qml.qrc

@@ -101,9 +101,11 @@
     </qresource>
     <qresource prefix="/icons">
         <file alias="add-wallet-dark">res/icons/add-wallet-dark.png</file>
+        <file alias="alert-filled">res/icons/alert-filled.png</file>
         <file alias="arrow-down">res/icons/arrow-down.png</file>
         <file alias="arrow-up">res/icons/arrow-up.png</file>
         <file alias="bitcoin-circle">res/icons/bitcoin-circle.png</file>
+        <file alias="blockclock-icon">res/icons/blockclock-icon.png</file>
         <file alias="blockclock-size-compact">res/icons/blockclock-size-compact.png</file>
         <file alias="blockclock-size-showcase">res/icons/blockclock-size-showcase.png</file>
         <file alias="blocktime-dark">res/icons/blocktime-dark.png</file>
@@ -114,6 +116,9 @@
         <file alias="caret-right">res/icons/caret-right.png</file>
         <file alias="check">res/icons/check.png</file>
         <file alias="copy">res/icons/copy.png</file>
+        <file alias="circle-file">res/icons/circle-file.png</file>
+        <file alias="circle-green-check">res/icons/circle-green-check.png</file>
+        <file alias="circle-red-cross">res/icons/circle-red-cross.png</file>
         <file alias="coinbase">res/icons/coinbase.png</file>
         <file alias="cross">res/icons/cross.png</file>
         <file alias="ellipsis">res/icons/ellipsis.png</file>
@@ -122,12 +127,15 @@
         <file alias="flip-vertical">res/icons/flip-vertical.png</file>
         <file alias="gear">res/icons/gear.png</file>
         <file alias="gear-outline">res/icons/gear-outline.png</file>
+        <file alias="green-check">res/icons/green-check.png</file>
         <file alias="hidden">res/icons/hidden.png</file>
         <file alias="info">res/icons/info.png</file>
         <file alias="lock">res/icons/lock.png</file>
         <file alias="minus">res/icons/minus.png</file>
         <file alias="network-dark">res/icons/network-dark.png</file>
         <file alias="network-light">res/icons/network-light.png</file>
+        <file alias="pending-dark">res/icons/pending-dark.png</file>
+        <file alias="pending-light">res/icons/pending-light.png</file>
         <file alias="plus">res/icons/plus.png</file>
         <file alias="plus-big-filled">res/icons/plus-big-filled.png</file>
         <file alias="pending">res/icons/pending.png</file>