[10.x] Add hasIndex and hasIndexes methods to Schema Builder

[liamkeily]

This PR introduces two new methods to the Schema builder: Schema::hasIndex($table, $index) and Schema::hasIndexes($table, $indexes). These methods align with the existing hasColumn and hasColumns methods as discussed on #49204 (comment)

Usage

Schema::hasIndex('user', 'email');

Schema::hasIndexes('user', ['email', 'name']);

Testing

Added unit tests, but also tested manually to ensure it actually works with real database

[morloderex]

@liamkeily This doesn't generate the index using the traditional naming conventions for indexes.

See the createIndexName method on the Illuminate\Database\Schema\Blueprint class.

Also we should probably allow specifying a type of index in order for this to work probably.

[taylorotwell]

Will let @hafezdivandari handle these methods.