Allow table name to be Symbol or String, remove run from macros

[matthewmcgarvey]

I had heard that using run in macros slowed down compilation times. Turns out, it's true!

I ran benchmarks on master and this branch (hyperfine --warmup 3 'crystal build --release spec/model_spec.cr')
master: 5.016 seconds (average)
with these changes: 4.156 seconds (average)

That's a 17% improvement in release compile time!

Changes

Our only use for run was to infer the table name in migrations and in the models. We turned the model name into a symbol that was the table name. We only ever needed this info at runtime so it made sense to bring the code that was in the file being run. The only problem is that we can't return a symbol anymore because the table name isn't determined until runtime and it's not possible to construct symbols at runtime. I added a TableName alias that is just String | Symbol and updated everywhere that takes in a table name to use it. I also found that all the places we were using Model::TABLE_NAME could be replaced by the class method Model.table_name so I removed the constant as well.

[jwoertink]

Yeah, I love this idea especially since speeding up the compile time can also help increase dev turn-around time.

I don't think we really lose any compile-time checks here because the schema enforcer should (in theory) be the one checking if you typed table "usres" instead of table "users", right?

[matthewmcgarvey]

Yep, no loss of safety, schema enforcer was already converting the symbol to a string https://www.github.com/luckyframework/avram/tree/master/src/avram/schema_enforcer/validation.cr