[Accessibility] Loading indicator aria labels (#166391)

## Summary

Closes #153597
In full screen, the loading indicator fails a11y tests. By removing the
aria-label and aria-hidden attributes, this allows the validation to
pass.
#153597 (comment)

This PR also introduces optional props for max and value props on the
`EuiProgress` component to provide consumers of the component greater
ability to define how the component is being used.
[Information](https://eui.elastic.co/#/display/progress#progress-with-values)
on the max and value props can be found in the [EUI
docs](https://eui.elastic.co/#/display/progress#progress-with-values).

---------

Co-authored-by: kibanamachine <[email protected]>

packages/core/chrome/core-chrome-browser-internal/src/ui/loading_indicator.tsx

@@ -19,6 +19,8 @@ export interface LoadingIndicatorProps {
   loadingCount$: ReturnType<HttpStart['getLoadingCount$']>;
   showAsBar?: boolean;
   customLogo?: string;
+  maxAmount?: number;
+  valueAmount?: string | number;
 }
 
 export class LoadingIndicator extends React.Component<LoadingIndicatorProps, { visible: boolean }> {
@@ -62,8 +64,6 @@ export class LoadingIndicator extends React.Component<LoadingIndicatorProps, { v
       ? 'globalLoadingIndicator'
       : 'globalLoadingIndicator-hidden';
 
-    const ariaHidden = !this.state.visible;
-
     const ariaLabel = i18n.translate('core.ui.loadingIndicatorAriaLabel', {
       defaultMessage: 'Loading content',
     });
@@ -107,8 +107,8 @@ export class LoadingIndicator extends React.Component<LoadingIndicatorProps, { v
       <EuiProgress
         className={className}
         data-test-subj={testSubj}
-        aria-hidden={ariaHidden}
-        aria-label={ariaLabel}
+        max={this.props.maxAmount}
+        value={this.props.valueAmount}
         position="fixed"
         color="accent"
         size="xs"