Enforce method order with ArchUnit

[bvkatwijk]

• Enforce alphabetical method order within method kinds:
  • static methods
  • non-static methods
  • adjusted return types

Notes:

• To interpret "adjusted return types" I currently used "All overridden methods", perhaps this is not fully accurate.
• ArchUnit does not yet have a built-in override predicate so I copied code from Failing to use Override annotaion as a Condition for ArchRule TNG/ArchUnit#359 (comment)
• Build will fail due to 264 detected violations
• Not yet done: Validating that entire sections are ordered (static methods > non-static methods > adjusted return types)

Example test output:

Architecture Violation [Priority: MEDIUM] - Rule 'classes should have methods alphabetically ordered in sections' was violated (264 times):
Methods in section 'adjusted return types' of class 'io.vavr.Function1$1' are not alphabetically ordered: [isDefinedAt, apply]

Part of implementing #2924