Add syscall for BLS aggregate signatures

[DrPeterVanNostrand]

This PR reopens the previously closed PR #1836.

[codecov-commenter]

Codecov Report

Merging #1914 (32a3281) into master (97b45db) will decrease coverage by 22.01%.
The diff coverage is 16.52%.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1914       +/-   ##
===========================================
- Coverage   75.45%   53.45%   -22.01%     
===========================================
  Files         156      156               
  Lines       15234    15357      +123     
===========================================
- Hits        11495     8209     -3286     
- Misses       3739     7148     +3409     

Files	Coverage Δ
fvm/src/kernel/mod.rs	0.00% <ø> (-83.34%)	⬇️
fvm/src/syscalls/mod.rs	0.00% <0.00%> (-96.88%)	⬇️
fvm/src/gas/price_list.rs	32.12% <0.00%> (-46.19%)	⬇️
fvm/src/syscalls/context.rs	51.61% <0.00%> (-45.56%)	⬇️
fvm/src/syscalls/crypto.rs	0.00% <0.00%> (-100.00%)	⬇️
shared/src/crypto/signature.rs	48.37% <54.92%> (-14.99%)	⬇️
fvm/src/kernel/default.rs	18.71% <0.00%> (-63.23%)	⬇️
sdk/src/crypto.rs	0.00% <0.00%> (ø)

... and 61 files with indirect coverage changes

[Stebalien]

Merged in #2003