Range operator

[brightening-eyes]

this is Range, now relative and absolute positional embeddings can be implemented better.

[codecov-commenter]

Codecov Report

Merging #5046 (f2c473d) into master (fdf2c48) will decrease coverage by 5.26%.
Report is 6 commits behind head on master.
The diff coverage is 78.04%.

@@             Coverage Diff             @@
##           master    #5046       +/-   ##
===========================================
- Coverage   94.72%   89.47%    -5.26%     
===========================================
  Files         765      307      -458     
  Lines      229654    89830   -139824     
===========================================
- Hits       217551    80373   -137178     
+ Misses      12103     9457     -2646     

Files Changed	Coverage Δ
src/layer/range.cpp	78.04% <78.04%> (ø)

... and 645 files with indirect coverage changes

[brightening-eyes]

@nihui
would you please review this?