Rename policy parameters

[erimatnor]

Policy parameters are renamed to be more consistent and intuitive
across different policies.

Fixes #2442

[erimatnor]

Note that reorder policy has no parameter for delayed reordering, so there was no parameter to rename to reorder_after as suggestion in issue #2442

[codecov]

Codecov Report

Merging #2458 into master will increase coverage by 0.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2458      +/-   ##
==========================================
+ Coverage   89.99%   90.10%   +0.11%     
==========================================
  Files         213      213              
  Lines       34406    34356      -50     
==========================================
- Hits        30964    30958       -6     
+ Misses       3442     3398      -44     

Impacted Files	Coverage Δ
src/copy.c	87.86% <ø> (-0.20%)	⬇️
src/indexing.c	94.87% <ø> (ø)
src/planner.c	93.80% <ø> (ø)
tsl/src/remote/dist_ddl.c	98.66% <ø> (ø)
src/cache_invalidate.c	84.44% <100.00%> (+0.72%)	⬆️
src/loader/bgw_launcher.c	89.53% <100.00%> (ø)
src/process_utility.c	93.70% <100.00%> (+<0.01%)	⬆️
tsl/src/fdw/shippable.c	82.85% <0.00%> (-11.43%)	⬇️
src/loader/bgw_message_queue.c	87.09% <0.00%> (ø)
src/import/planner.c	69.54% <0.00%> (+10.37%)	⬆️

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[pmwkaa]

Do we need any renames in the corresponding C functions as well?