imgtool: dumpinfo improvements

Fix trailer info dumping reads pad characters as values for status
Refactor printing styled texts and frames
Use isinstance() for type checking
Fold notice text depending on line length
Refactoring some parts for readability
Fix additional linting issues

Signed-off-by: Rustam Ismayilov <rustam.ismayilov@arm.com>
Change-Id: I741562bb70b18407bdd32e9c7391048faf6394c6