[shell][zsh] Don't resolve symlinks in ALT-c (#4816)

This way ALT-c behaves more aligned with `cd`.

Imagine a setup like:
```
/foo -> foo_real
/foo_real/bar
```

Right now if we first `cd foo` (a symlink to `foo_real`), and
then use ALT-c to goto `bar`, then we would end up executing
`cd /foo_real/bar` instead of `cd /foo/bar`. `$PWD = /foo_real/bar`.

For comparison, if we first `cd foo` and then `cd bar`, we end up with
`$PWD = /foo/bar`.

This commit changes the internal logic of `fzf-cd-widget` to first run
`cd <result of FZF_ALT_C_COMMAND>` in a subshell to simulate the
behavior of `cd`, and then insert the target PWD into the shell history.
This way we get behavior consistent with the builtin `cd` command, while
also recording reusable shell history.

shell/key-bindings.zsh

@@ -110,8 +110,14 @@ fzf-cd-widget() {
     zle redisplay
     return 0
   fi
+  # Use subshell expansion to get the absolute PWD of the target dir.
+  # This allows the recorded shell history to be reused even from a different
+  # working directory.
+  # If failed, fallback to the unexpanded path to surface the error to the user.
+  # NOTE: Don't use the `:a` modifier as it resolves symlinks like `pwd -P`.
+  dir=$(builtin cd >/dev/null -- "${dir}" && echo "${PWD}" || echo "${dir}")
   zle push-line # Clear buffer. Auto-restored on next prompt.
-  BUFFER="builtin cd -- ${(q)dir:a}"
+  BUFFER="builtin cd -- ${(q)dir}"
   zle accept-line
   local ret=$?
   unset dir # ensure this doesn't end up appearing in prompt expansion