[5.6] Fix JSON queries with table names on SQL Server

[staudenmeir]

JSON queries on SQL Server don't yet support columns with table names:

DB::table('users')->where('users.options->language', 'en')->get();
DB::table('users')->whereJsonContains('users.options->languages', 'en')->get();

Table names have been broken because JSON queries work differently on SQL Server: While MySQL and PostgreSQL use the arrow operator (column->path), SQL Server uses JSON functions.
This led to incorrect SQL: where [users].json_value([options], '$."language"') = ?.

Unfortunately, the fix requires some refactoring. We have to move the use of wrapJsonSelector() from wrapValue() up to wrap(). We could integrate it into Database\Grammar::wrap(), but I think that it rather belongs into Database\Query\Grammars\Grammar since it doesn't concern Schema grammars.

I also used the opportunity to improve the SQL Server grammar by extracting wrapJsonPath(). It's a better solution than replacing the names of JSON functions in SQL strings.

I added table name tests for all databases.

The PR is also a preparation for supporting JSON queries on MariaDB (laravel/ideas#811):
When replacing MySQL's arrow operator with the equivalent JSON_EXTRACT(), we would have run into the same wrapping problems.

[taylorotwell]

Do you use SQL Server professionally on a daily basis?

[staudenmeir]

I use SQL Server for one project, the rest is MySQL. So rather weekly than daily.

[taylorotwell]

It looks like this changes the behavior of MySQL wrapping as well?

[staudenmeir]

Do you mean the code changes in MySqlGrammar? Or that the generated SQL changes?

[taylorotwell]

Well you change existing MySQL tests here:

[staudenmeir]

I added table name tests for the other databases to catch bugs like this in the future.