message: refactor(sg): add comments for ICMP type/code negative values in IPv6
diff: <td class="mat-cell">
  <ng-container *ngIf="protocol === NetworkProtocols.ICMP">
  <mat-form-field floatPlaceholder="never">
  + <!-- From CloudStack docs: The ICMP type (if protocol=ICMP). A value of -1 means all types. -->
  <input
  matInput
  maxValue="255"
  name="startPort"
  type="number"
  [(ngModel)]="startPort"
  - [minValue]="0"
  - [maxValue]="65535"
  + minValue="0"
  + maxValue="65535"
  [placeholder]="'SECURITY_GROUP_PAGE.RULES.START_PORT' | translate"
  integerValue
  required
  <td class="mat-cell">
  <ng-container *ngIf="protocol === NetworkProtocols.ICMP">
  <mat-form-field floatPlaceholder="never">
  + <!-- From CloudStack docs: -->
  + <!-- The ICMP code (if protocol=ICMP). A value of -1 means all codes for the given ICMP type. -->
  <input
  matInput
  name="icmpCode"
  name="endPort"
  type="number"
  [(ngModel)]="endPort"
  - [minValue]="0"
  - [maxValue]="65535"
  + minValue="0"
  + maxValue="65535"
  [placeholder]="'SECURITY_GROUP_PAGE.RULES.END_PORT' | translate"
  integerValue
  required
  <mat-icon *ngIf="!adding">add</mat-icon>
  <mat-spinner
  *ngIf="adding"
  - [diameter]="25"
  - [strokeWidth]="5"
  + diameter="25"
  + strokeWidth="5"
  ></mat-spinner>
  </button>
  </td>
  