Fix crashes caused by empty pedigrees

[reedacartwright]

dng::io::BamPileup::SelectLibraries forgets to clear the read_group_to_libraries_ map, resulting in invalid or out-of-date indexes being returned to connect read-groups to libraries.

dng::io::BamPileup now requires RG information for reads, which means that specifying one file per read-group is no longer supported. This feature had not been well maintained or supported through version, so I am retiring it.

dng::io::VcfPileup::SelectLibraries now passes nullptr to bcf_hdr_set_samples to remove all samples from the input. This prevents a cryptic error message.

Tests were added to DngCall to verify that the crashes are fixed. This requires an update of TESTDATA information.

[codecov[bot]]

Codecov Report

Merging #230 into develop will increase coverage by 0.1%. The diff coverage is 37.5%.

@@            Coverage Diff            @@
##           develop    #230     +/-   ##
=========================================
+ Coverage    66.99%   67.1%   +0.1%     
=========================================
  Files           70      70             
  Lines         6517    6520      +3     
  Branches      1139    1140      +1     
=========================================
+ Hits          4366    4375      +9     
+ Misses        1688    1684      -4     
+ Partials       463     461      -2

Impacted Files	Coverage Δ
src/include/dng/io/bcf.h	64.81% <0%> (-0.9%)	:arrow_down:
src/include/dng/io/bam.h	72% <100%> (+2.26%)	:arrow_up:
src/lib/bam.cc	77.98% <50%> (+1.12%)	:arrow_up:
src/lib/relationship_graph.cc	72.14% <0%> (+0.16%)	:arrow_up:
src/lib/task/call.cc	81.81% <0%> (+0.4%)	:arrow_up:
src/include/dng/library.h	55.55% <0%> (+22.22%)	:arrow_up:

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