ENH: Add an extension point on `getReportField`

[mikenuguid]

Description

Add an extension on the getReportField() on both report classes ElementsInUseReport and ElementTypeReport to allow easier updates on gridfield components e.g. implementing GridFieldQueuedExportButton to allow csv export using queuedjob.

Example:

public function getReportField()
{
    Requirements::css('dnadesign/silverstripe-elemental:client/dist/styles/bundle.css');

    /** @var GridField $field */
    $field = parent::getReportField();
    $field->addExtraClass('elemental-report__grid-field');

    $this->extend('updateReportField', $field);

    return $field;
}

Additional context or points of discussion

No response

Validations

• [X] You intend to implement the feature yourself
• [X] You have read the contributing guide
• [X] You strongly believe this feature should be in core, rather than being its own community module
• [X] You have checked for existing issues or pull requests related to this feature (and didn't find any)

[GuySartorelli]

You can get and manipulate the report field using the updateCMSFields extension hook. I don't see that adding an extension hook specifically to getReportField() would be a significant improvement. I'm going to close this issue on that basis.

If you can show that there is a significant improvement by adding extension hooks to getReportField() then we can discuss further.