Tidy LegacyMockInterface

[davedevelopment]

This might need splitting further. Ideally any "internal" methods, i.e. those we use to manage and run the doubles, shouldn't be exposed in the interface.

It would be nice to update the return types (either in the code itself or in the PHPStorm Meta), so that it's clear that the various factory methods return a union type of the class the user specifies, along with the methods mockery makes available to them, but not the internal rubbish like mockery_getContainer etc.

With:

override(\spy(0), map(["" => "@|Mockery\MockInterface"]));

I currently see:

The MockInterface extends LegacyMockInterface might still be useful to keep (see #861), but it's messy, and it might be time to cut those people loose, or provide a better alternative.

[ghostwriter]

• Partially addressed in Update PHPStorm metadata to support Intersection Types #1231.

• The deprecation 1.5.x|1.6.x and removal 2.0.x of the mockery_*() internal methods

• Add doc comments to indicate intersection types for static analysis tools.

/** 
* @template T of object
* @return T&\Mockery\MockInterface
*/