Fix CI_SPLIT for base case test matrix

[randomanderson]

What Does This Do

Properly runs tests using the default test_matrix.

There's an interaction where parallel isn't being used for test splitting but just for separate jvms. he script sees CI_NODE_TOTAL=12 and CI_NODE_INDEX=1, because is a test_matrix (8, 11, 17, etc). It then uses our modulo test splitting to assign tests to nodes and sees that no tests are assigned to the current node. By explicitly setting 1/1, no tests are improperly skipped.

Motivation

For test_debugging and test_profiling, many tests were skipped that should not have been.

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Jira ticket: [PROJ-IDENT]