Description of proposed changes

This PR adds support for loading the SNAPHU-generated connected components for Gamma interferogram stacks, thereby allowing unwrapping error corrections for Gamma products, as requested by @AoqingGuo-Ucb in #1375. Detailed changes are:

• cli.prep_gamma.py: add .conncomp to the supported file extension

• prep_gamma.py: add special treatment in the lks and DATA_TYPE extraction for the connected component file

• utils.readfile.get_slice_list(): return only ["phase"] if there is only one band, such as the case of gamma .unw file.

Reminders

• Fix [Unwrapping Error Correction] Unsupported .conncomp file format causes smallbaselineApp.py to fail #1375
• Pass Pre-commit check (green)
• Pass Codacy code review (green)
• Pass Circle CI test (green)
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Summary by Sourcery

Enable support for SNAPHU-connected component (.conncomp) files in Gamma interferogram preprocessing, including CLI recognition, metadata handling, and phase-only data slicing.

New Features:

• Recognize .conncomp files in the CLI and include them in the supported input extensions
• Extend metadata extraction to handle .conncomp files by adjusting look parameter parsing and setting DATA_TYPE to BYTE

Enhancements:

• Return only the phase band when reading single-band Gamma .unw files

Documentation:

• Update CLI help text and examples to mention .conncomp and its corresponding .rsc file