The function `populate_symlink_workdir` creates a new
"symlink.git" repository with a relative path "../symlink.git".
As the current working directory is the sandbox, the new
repository will be created just outside of the sandbox.

Fix this by using `clar_sandbox_path`.

Move to the `git_error` name in the internal API for error-related
functions.

Update internal usage to use the `git_reference` names for constants.

Wrap function calls in the `checkout::crlf` tests with `cl_git_pass`,
`cl_assert`, etc. to ensure that they're successful.

After sandboxing the crlf directory, remove the working directory
contents.  This allows us to package data within the crlf directory
(for simplicity, this allows us to script the to-odb and to-workdir
crlf filter conversion data in a single location).

Move the crlf_data folders reponsible for holding the state of the
filters going into the working directory to "to_workdir" variations of
the folder name to accommodate future growth into the "to odb" filter
variation.  Update the script to create these new folders as appopriate.

Use the new object_type enumeration names within the codebase.

Use the new-style index names throughout our own codebase.

Test updated symbolic link creation on Windows.  Ensure that we emulate
Git for Windows behavior.  Ensure that when `core.symlinks=true` is set
in a global configuration that new repositories are created without a
`core.symlinks` setting, and that when `core.symlinks` is unset that
`core.symlinks=false` in set in the repository.  Further ensure that
checkout honors the expected `core.symlinks` defaults on Windows.