Fix promoted tspan for BVProblem and ODEProblem

[codecov[bot]]

Codecov Report

Merging #474 (6bf34a8) into master (5d0b887) will increase coverage by 9.44%. Report is 3 commits behind head on master. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #474      +/-   ##
==========================================
+ Coverage   47.17%   56.61%   +9.44%     
==========================================
  Files          47       47              
  Lines        3572     3582      +10     
==========================================
+ Hits         1685     2028     +343     
+ Misses       1887     1554     -333     

Files Changed	Coverage Δ
src/ensemble/ensemble_problems.jl	42.85% <ø> (+19.04%)	:arrow_up:
src/problems/bvp_problems.jl	56.66% <ø> (+12.66%)	:arrow_up:
src/problems/ode_problems.jl	56.41% <100.00%> (+2.56%)	:arrow_up:

... and 22 files with indirect coverage changes

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[ChrisRackauckas]

This needs a test.