CPP-972: make expected_message more generic so it can match C* 4.0 re…

[weideng1]

…sult.error_message in test ServerSideFailureTests.Integration_Cassandra_ErrorFunctionAlreadyExists

[absurdfarce]

I think we can make this test quite a bit more granular and still keep it passing across all tested Cassandra versions.

[absurdfarce]

I feel like we might be losing specificity here when we don't necessarily have to:

[cqlsh 6.0.0 | Cassandra 4.0.2 | CQL spec 3.4.5 | Native protocol v5]
Use HELP for help.
cqlsh> use ks;
cqlsh:ks> CREATE FUNCTION already_exists_function(value double) RETURNS NULL ON NULL INPUT RETURNS double LANGUAGE java AS 'return 3.14;' ;
cqlsh:ks> CREATE FUNCTION already_exists_function(value double) RETURNS NULL ON NULL INPUT RETURNS double LANGUAGE java AS 'return 3.14;' ;
InvalidRequest: Error from server: code=2200 [Invalid query] message="Function 'already_exists_function' already exists"

[cqlsh 5.0.1 | Cassandra 3.11.15 | CQL spec 3.4.4 | Native protocol v4]
Use HELP for help.
cqlsh> use testy;
cqlsh:testy> CREATE FUNCTION already_exists_function(value double) RETURNS NULL ON NULL INPUT RETURNS double LANGUAGE java AS 'return 3.14;' ;
cqlsh:testy> CREATE FUNCTION already_exists_function(value double) RETURNS NULL ON NULL INPUT RETURNS double LANGUAGE java AS 'return 3.14;' ;
InvalidRequest: Error from server: code=2200 [Invalid query] message="Function testy.already_exists_function : (double) -> double already exists"

Seems like what we really want to check for here is something like "Function(.)already_exists_function(.) already exists". We should be able to do that via something like:

• Get the position of "Function" as pos1
• EXPECT_TRUE(pos1 != npos)
• Get the position of the function name as pos2
• EXPECT_TRUE(pos2 != npos)
• EXPECT_TRUE(pos2 > pos1) (since it should always come after it in the string)
• Get the position of " already exists" as pos3
• EXPECT_TRUE(pos3 != npos)
• EXPECT_TRUE(pos3 > pos2) (as above)