[Log Explorer] Update minimum height for JSON doc view (elastic#171553)

## 📓 Summary

Closes elastic#171485 

This fix guarantees the JSON doc view will always get a minimum space
independently of the available space, to avoid the current scenario
where a scrollable flyout does not reserve enough space for the JSON tab
content tobe displayed (see recording in the related issue).


https://github.com/elastic/kibana/assets/34506779/2c539047-32cd-4213-bc6f-3062de151426

---------

Co-authored-by: Marco Antonio Ghiani <[email protected]>

src/plugins/unified_doc_viewer/public/components/doc_viewer_source/get_height.test.tsx

@@ -12,13 +12,13 @@ import { getHeight } from './get_height';
 describe('getHeight', () => {
   Object.defineProperty(window, 'innerHeight', { writable: true, configurable: true, value: 500 });
 
-  const getMonacoMock = (lineCount: number) => {
+  const getMonacoMock = (lineCount: number, top: number = 200) => {
     return {
       getDomNode: jest.fn(() => {
         return {
           getBoundingClientRect: jest.fn(() => {
             return {
-              top: 200,
+              top,
             };
           }),
         };
@@ -29,10 +29,17 @@ describe('getHeight', () => {
     } as unknown as monaco.editor.IStandaloneCodeEditor;
   };
   test('when using document explorer, returning the available height in the flyout', () => {
+    const monacoMock = getMonacoMock(500, 0);
+
+    const height = getHeight(monacoMock, true);
+    expect(height).toBe(475);
+  });
+
+  test('when using document explorer, returning the available height in the flyout has a minimun guarenteed height', () => {
     const monacoMock = getMonacoMock(500);
 
     const height = getHeight(monacoMock, true);
-    expect(height).toBe(275);
+    expect(height).toBe(400);
   });
 
   test('when using classic table, its displayed inline without scrolling', () => {

src/plugins/unified_doc_viewer/public/components/doc_viewer_source/get_height.tsx

@@ -6,7 +6,7 @@
  * Side Public License, v 1.
  */
 import { monaco } from '@kbn/monaco';
-import { MARGIN_BOTTOM, MAX_LINES_CLASSIC_TABLE } from './source';
+import { MARGIN_BOTTOM, MAX_LINES_CLASSIC_TABLE, MIN_HEIGHT } from './source';
 
 export function getHeight(editor: monaco.editor.IStandaloneCodeEditor, useDocExplorer: boolean) {
   const editorElement = editor?.getDomNode();
@@ -28,5 +28,5 @@ export function getHeight(editor: monaco.editor.IStandaloneCodeEditor, useDocExp
       lineCount > MAX_LINES_CLASSIC_TABLE ? MAX_LINES_CLASSIC_TABLE : lineCount;
     result = editor.getTopForLineNumber(displayedLineCount + 1) + lineHeight;
   }
-  return result > 0 ? result : 0;
+  return Math.max(result, MIN_HEIGHT);
 }

src/plugins/unified_doc_viewer/public/components/doc_viewer_source/source.tsx

@@ -36,6 +36,8 @@ interface SourceViewerProps {
 export const MAX_LINES_CLASSIC_TABLE = 500;
 // Displayed margin of the code editor to the window bottom when rendered in the document explorer flyout
 export const MARGIN_BOTTOM = 25;
+// Minimum height for the source content to guarantee minimum space when the flyout is scrollable.
+export const MIN_HEIGHT = 400;
 
 export const DocViewerSource = ({
   id,