Allow to customize the approval files location from annotations in the code

[aneveux]

Instead of putting all the approved files in src/test/resources in folders named after the FQN of the class and creating files named after each method, annotations should allow the user to customize the location of generated files:

@ApprovalFiles("src/approvals/files")
class TestFoo {
 @ApprovalFile("barFile")
 @Test
 void bar() {
 Approvals.verify(...);
 }
}

Should allow me to have the generated approved and received files located in src/approvals/files/barFile.