feat: Watermarks with alpha support and respect to ratio (DEV-4072)

[siers]

• Alpha support for watermarks added.
• Serialized TIFF in tests and checked that the watermark is applied by checking against a similarity index.
• Stable watermark position after cropping is unfortunately not supported.
  • Due to progressive loading in JPEG2000, applying the watermark before transformations is not possible.

[linear]

DEV-3299 Sipi should overlay the watermark by adhering to the aspect ratio

DEV-4072 Support HEAD requests for IIIF URLs in SIPI

[codecov]

Codecov Report

Attention: Patch coverage is 82.75862% with 5 lines in your changes missing coverage. Please review.

Project coverage is 22.6%. Comparing base (f3a9a96) to head (83e5aea).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/SipiImage.cpp	82.7%	2 Missing and 3 partials ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/SipiImage.hpp	24.6% <ø> (ø)
src/formats/SipiIOTiff.cpp	29.1% <ø> (-0.1%)	⬇️
src/SipiImage.cpp	24.2% <82.7%> (+0.8%)	⬆️

... and 4 files with indirect coverage changes

[subotic]

Thanks. Good work!