More simpler regexp to match different class declarations and slight refactoring in the Python parser

Tested class declarations:

class Philosopher:
class AustralianPhilosopher(Philosopher, default_name="Bruce"):
class Meta():
class MyClass(metaclass=Meta):
class MySubclass(MyClass):

Fix case where AustralianPhilosopher is not detected

Also, slight refactoring about:

• replace QLatin1String by QStringLiteral where relevant to avoid cast
• use static const for QRegularExpression variables and move out of the loop
• replace variable use to define the type of the symbol by a class enum
• create a directory where sample test files are stored (and add a sample test file for Python)

ISSUE: #75 (closed)

BUG: 454545