t1092: replace 'read-cache --table' with 'ls-files --sparse'

t1092: replace 'read-cache --table' with 'ls-files --sparse'

Now that 'git ls-files --sparse' exists, we can use it to verify the
state of a sparse index instead of 'test-tool read-cache table'. Replace
these usages within t1092-sparse-checkout-compatibility.sh.

The important changes are due to the different output format. We need to
use the '--stage' output to get a file mode and OID, but it also
includes a stage value and drops the object type. This leads to some
differences in how we handle looking for specific entries.

Some places where we previously looked for no 'tree' entries, we can
instead directly compare the output across the repository with a sparse
index and the one without.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>