Delete 20 orphan files, replace Maths.hypot with Math.hypot (3308 lines)

Removed files with zero external consumers:
- 4 rgroup files (ECRgroupFrequency, FingerprintType, etc.)
- 3 container files (MolContainer, FingerPrintContainer, ReactionInfoCollector)
- 3 interface files (IMolDescriptors, IInChIContainer, ITransformation)
- 2 labelling files (AbstractReactionLabeller, ICanonicalReactionLabeller)
- Plus RxnDecoderOptions, IFingerprinter, EnumBondTypeChange,
  RXNFileImporter, Distance, Maths, SignatureMoleculeLabeller

Replaced custom Maths.hypot wrapper with java.lang.Math.hypot in
4 matrix decomposition files. All 135 tests pass.

Co-Authored-By: Syed Asad Rahman <asad.rahman@bioinceptionlabs.com>

Author: asad