chore: replace ObjectStore type requirement with ObspecInput

[hrodmn]

resolves #28

[github-actions]

Benchmark Comparison

Test	Baseline (ms)	PR (ms)	Change
test_band_access_pattern[multi_band]	1325.1	1316.1	-0.7%
test_band_access_pattern[single_band]	1202.6	1215.1	+1.0%
test_full_compute	627.2	685.9	+9.4%
test_mosaic_method[first]	613.3	647.2	+5.5%
test_mosaic_method[median]	641.4	670.3	+4.5%
test_native_crs_resolution	10757.3	10729.2	-0.3%
test_open_overhead	270.5	277.3	+2.5%
test_reproject_workers[1]	1354.0	1336.8	-1.3%
test_reproject_workers[4]	1348.5	1342.9	-0.4%
test_time_step_parallelism[dask_time_1]	1331.2	1318.1	-1.0%
test_time_step_parallelism[no_dask]	914.6	926.9	+1.3%