Add test for capitalized Soong config variable

Soong config variables come from Make where they might be capitalized,
but Blueprint didn't handle capitalized variables well.  Add test
coverage for capitalized Soong config variables.

Bug: 148865218
Test: soong_config_module_test.go
Change-Id: I1e434e392d5ee660a221a0d3f959811c35e65865