[Mirror] Fix assert_defined

[csiefer2]

Automated mirror of upstream PR trilinos#15114 ## Motivation
It looks like assert_defined only asserts that the first variable is defined..

[gemini-code-assist]

Code Review

This pull request refactors ASSERT_DEFINED calls across numerous CMakeLists.txt files to assert variables individually rather than passing multiple arguments to a single call. This pattern is applied throughout various packages such as MueLu, Stokhos, and Thyra. Feedback indicates that in packages/nox/test/epetra/Thyra/CMakeLists.txt, some calls still contain multiple variables, which should be split into individual assertions to ensure all variables are properly checked.

[gemini-code-assist]

The pull request description states that ASSERT_DEFINED only asserts the first variable. However, these lines still contain multiple arguments, meaning NOX_ENABLE_EpetraExt and Stratimikos_ENABLE_AztecOO will not be checked. These should be split into individual calls to ensure all variables are properly asserted.

ASSERT_DEFINED(NOX_ENABLE_Epetra)
ASSERT_DEFINED(NOX_ENABLE_EpetraExt)
ASSERT_DEFINED(NOX_ENABLE_Stratimikos)
ASSERT_DEFINED(Stratimikos_ENABLE_AztecOO)

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