Change some test EXPECT to ASSERT to avoid segfaults

Merge from Widevine repo of http://go/wvgerrit/94505

Some tests use an EXPECT when checking an array size or to verify a
pointer is not null. Then they access the pointer or array. When they
use an EXPECT, this access results in a segfault.

I also removed a compiler warning about unused parameters.

Bug: 149856581
Test: request_license_test (now lists failed tests)
Change-Id: I08ac11250921245c89ed5c0c43cc5f4321e0a9cc

libwvdrmengine/cdm/core/test/usage_table_header_unittest.cpp

@@ -437,7 +437,7 @@ class MockCryptoSession : public TestCryptoSession {
 
   // Fake method for testing.  Having an EXPECT_CALL causes complexities
   // for getting table capacity during initialization.
-  virtual bool GetMaximumUsageTableEntries(SecurityLevel security_level,
+  virtual bool GetMaximumUsageTableEntries(SecurityLevel /*security_level*/,
                                            size_t* number_of_entries) {
     if (number_of_entries == nullptr || !maximum_usage_table_entries_set_)
       return false;