Change behavior of Param::Get<bool>

[scpeters]

🦟 Bug fix

Implements a behavior change from a TODO comment in the Fortress era

Summary

A comment was added in d353294 to #638 suggesting a behavior change in Param::Get<bool> that should be done for Fortress. I just noticed it recently and have implemented the behavior change and updated a test and the migration guide.

Description of behavior change:

Previously when a Param was set from a string, the
Get<bool> method would always return true, and
the value would be true if the lowercase value string
matched "1" or "true". Otherwise the value would
be false.

Now, the Get<bool> method returns true only if the
lowercase value string matches one of "0", "1",
"true", or "false". Otherwise Get<bool> returns
false and the value is not written.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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