Add direct coordinate descent minimizer tests

Cover independent blocks, coupled block ordering, and an excluded
block with analytic residuals. Check automatic ordering and restored
parameter metadata.

Initialize state and metadata before minimizer initialization. Reset
saved state before repeated solves. Check nonzero metadata restoration
in the repeated and exclusion cases.

The isolated test binary compiled against retained CPU libraries.
All eight discovered cases passed.

Issue: https://github.com/ceres-solver/ceres-solver/issues/938

Codex used.

Change-Id: Ice01781aa114e80d867feadd77d4f52da7a46dcc