demonstration of inline projection for sort

[SunRunAway]

What problem does this PR solve?

demonstration of inline projection for sort

1. Planner: prune output columns in LogicalSort
2. Executor: do not copy columns that output doesn't need in SortExec

What is changed and how it works?

name                                                   old time/op    new time/op    delta
SortExec/(rows:3000000,_orderBy:[0],_output:[1_2])-12     4.27s ± 3%     4.04s ± 3%   -5.48%  (p=0.016 n=5+5)
SortExec/(rows:3000000,_orderBy:[0],_output:[1])-12       4.26s ± 2%     3.83s ± 3%  -10.02%  (p=0.008 n=5+5)

name                                                   old alloc/op   new alloc/op   delta
SortExec/(rows:3000000,_orderBy:[0],_output:[1_2])-12    27.9MB ± 0%    27.9MB ± 0%   -0.13%  (p=0.008 n=5+5)
SortExec/(rows:3000000,_orderBy:[0],_output:[1])-12      27.9MB ± 0%    27.8MB ± 0%   -0.26%  (p=0.008 n=5+5)

name                                                   old allocs/op  new allocs/op  delta
SortExec/(rows:3000000,_orderBy:[0],_output:[1_2])-12     41.1k ± 0%     41.1k ± 0%   -0.03%  (p=0.029 n=4+4)
SortExec/(rows:3000000,_orderBy:[0],_output:[1])-12       41.1k ± 0%     41.1k ± 0%   -0.07%  (p=0.029 n=4+4)

[SunRunAway]

It's just for demonstration. Will create a proposal.