[bugfix] Check for {{bots}}/{{nobots}} in Page.text setter

This reverts fdfae7bb446a6 and moves early check into BasePage.text setter

• revert fdfae7bb446a6 change for BasePage
• check for botMayEdit in text setter first but ignore DryRequest rejecting Exception
• update old tests with those steps:
  • call text deleter to remove "_raw_extracted_templates" cache
  • add template to "_text" attribute directly to bypass the botMayEdit check
  • make the test
  • clear the botMayEdit cache

Bug: T267770
Change-Id: I03f23af85371d4246f41db70c7148a27d9b34c35