Move about 50 test files related to basic layout, packing, alignment,
sections, and image structure into a pack/ subdirectory. Drop the
numeric prefixes from the filenames and update all references in
ftest.py, entry_test.py, and binman_tests.rst

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

Binman lets us declare symbols in SPL/TPL that refer to other entries in
the same binman image as them. These symbols are filled in with the
correct values while binman assembles the images, but this is done
in-memory only. Symbols marked as optional can be filled with
BINMAN_SYM_MISSING as an error value if their referred entry is missing.

However, the unmodified SPL/TPL binaries are still available on disk,
and can be used by people. For these files, nothing ensures that the
symbols are set to this error value, and they will be considered valid
when they are not.

Empirically, all symbols show up as zero in a sandbox_vpl build when we
run e.g. tpl/u-boot-tpl directly. On the other hand, zero is a perfectly
fine value for a binman-written symbol, so we cannot say the symbols
have wrong values based on that.

Declare a magic symbol that binman always fills in with a fixed value.
Check this value as an indicator that symbols were filled in correctly.
Return the error value for all symbols when this magic symbol has the
wrong value.

For binman tests, we need to make room for the new symbol in the mocked
SPL/TPL data by extending them by four bytes. This messes up some test
image layouts. Fix the affected values, and check the magic symbol
wherever it makes sense.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>

At present these are large enough to hold 20 bytes of symbol data. Add
four more bytes so we can add another test.

Unfortunately at present this involves changing a few test files to make
room. We could adjust the test files to not specify sizes for entries.
Then we could make the tests check the actual sizes. But for now, leave it
as it is, since the effort is minor.

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

We now have 99 tests. Before adding any more, rename everything to three
digits. This helps to preserve the ordering of tests and makes it easier
to find things.

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