feat(diagnostic_graph_utils): publish error graph instead of the terminal log

[takayuki5168]

Description

The diag_graph_utils's output to the terminal is a bit too frequent to fill the whole terminal screen. Instead of the output to the terminal, this PR makes the diag_graph_utils publish the string message of the error diag graph so that the Rviz can visualize it as follows.

Related links

How was this PR tested?

psim worked well

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

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