Print last directory and selections to stdout instead of file

[joelim-work]

• Fixes lfcd improvement proposal #1393

Changes:

• -last-dir-path and -selection-path options are now replaced with -last-dir and -selection, which print the information to stdout instead of a file. This is a breaking change.
• Output from running shell commands is now connected to stderr instead of stdout if either of the above options are provided.
• Shell completions are updated.
• The various implementations of lfcd are updated to consume the output of lf directly instead of having to create and read from a temp file.
• The lf.vim plugin is also updated to similarly read directly from lf instead of a temp file.

I have done some testing on each of these setups, although I would greatly appreciate it if others helped to test as well, as the testing surface area is quite large and I may have missed something. For this reason I am also marking this PR as a draft.