update default parameters for discrete consistency model

[arrjon]

This pull request updates the ConsistencyModel implementation in consistency_model.py to improve flexibility. The main changes include parameterization of previously hardcoded constants, improved handling of discretization steps, improved default parameters and enhanced warnings for suboptimal sampling configurations.

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...rks/consistency_models/stable_consistency_model.py	0.00%	4 Missing ⚠️
...w/networks/consistency_models/consistency_model.py	91.66%	2 Missing ⚠️

Files with missing lines	Coverage Δ
...w/networks/consistency_models/consistency_model.py	96.89% <91.66%> (-1.47%)	⬇️
...rks/consistency_models/stable_consistency_model.py	22.33% <0.00%> (ø)

... and 5 files with indirect coverage changes