vim-patch:8.2.{3468,3617,3618,3622}: some other CWD related patches

Problem:    "verbose pwd" shows confusing info when :lcd does not change
            directory.
Solution:   Clear last_chdir_reason also when the directory does not change.
            (closes vim/vim#9160)
https://github.com/vim/vim/commit/64be6aa3a54ecfe355d4a03e1200650c301e7f29

This only ports the tests, as this is already Nvim's behavior.

Problem:    ":verbose pwd" does not mention 'autochdir' was applied.
Solution:   Remember the last chdir was done by 'autochdir'.  (issue vim/vim#9142)
https://github.com/vim/vim/commit/0526815c15170a5926e1008600ec29d42d8b64c2

Problem:    Problem with :cd when editing file in non-existent directory. (Yee
            Cheng Chin)
Solution:   Prepend the current directory to get the full path. (closes vim/vim#8903)
https://github.com/vim/vim/commit/c6376c798433bcb9ee38a8664299d11454546950

Adds method call support for all functions in the patch, but it cannot
be fully ported due to missing tests for:

- index(): requires Blobs from v8.1.0735.
           Note that index() was already added as a method in v8.1.1803;
           this patch only adds a test.

- iconv(): requires v8.1.1136 for test_termcodes.vim.

Nvim deprecated inputdialog(), so it no longer has an eval.txt entry.

Keep the test for hlexists() commented-out, just like previously. (Nvim
always defines the Number group, so it always returns 1 instead)

Cannot include both changes to test_syn_attr.vim as Nvim doesn't support
":hi term=..."; however, both test the same ->hlID() syntax anyway.

Adds method call support for all functions in the patch, but it cannot
be fully ported due to missing tests for:

- getcwd(): requires chdir() and Test_chdir_func() from v8.1.1291.

Note that the method call tests for getreg() and getregtype() were
removed in v8.2.1547, which has already been ported, but doesn't seem to
have been replaced with a new test...

This patch also makes getchangelist()'s argument optional (defaults to
the current buffer).

eval.txt includes a typo for gettabwinvar(), which is fixed in
v8.1.1952.