Move the remaining 60 or so test files into an entry/ subdirectory.
These cover general entry types and features: entry args, fill, text,
env, compress, replace, template, collection, ELF, overlap, listing,
sections, symlink, TEE OS, and other miscellaneous entries. Drop the
numeric prefixes and update all references.

Signed-off-by: Simon Glass <simon.glass@canonical.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>

While it is useful and efficient to build images in a single pass from a
unified description, it is sometimes desirable to update the image later.

Add support for replace an existing file with one of the same size. This
avoids needing to repack the file. Support for more advanced updates will
come in future patches.

Signed-off-by: Simon Glass <sjg@chromium.org>