feat(restack): Add --as argument for bulk topic reordering

[ashelly]

Add restack --as to reorder topics into a chain, updating Relative: tags.

Topic: add_restack_as
Relative: create_relative_utils

[ashelly]

Reviews in this chain:
└#18 Feature: common utils for end-to-end tests
　├#10 Feature: Tree command to Show Stack
　│├#19 Feature: Tests for tree (stack show) command
　│└#9 feat(edit): Add revup edit command with safety features
　│　└#12 test(edit): Add tests for edit safety features
　│　　└#21 Docs: Describe new features
　└#3 Feature: Revup commit gains --topic and --relative to pre-populate commit message
　　└#13 feat(utils): Create relative_utils module for topic relationship management
　　　├#14 Feature: amend --relative fixes stack
　　　│├#17 Tests(amend): Tests for amend behavior, especially --relative
　　　│└#4 Feature: Revup commit gains --draft flag
　　　│　└#20 Feature: tests for the --draft flag
　　　└#15 feat(restack): Add --as argument for bulk topic reordering
　　　　└#16 test(restack): Add tests for --as argument and GCA algorithm

[ashelly]

#	head	base	diff	date	summary
0	a283ffbe	3171aa70	diff	Feb 4 14:23 PM	4 files changed, 163 insertions(+), 1 deletion(-)