Multiple filters error - 'filters' option overwritten

Problem/Motivation

Currently, if there are multiple filters on indexed fields for a Search API view using an Algolia index, the foreach loop in SearchApiAlgoliaBackend::extractConditions overwrites $options['filters'] on each pass, resulting in invalid syntax and an error message `filters: Unexpected token 'AND' expected filter at col 1`.

Steps to reproduce

Create a view of an Algolia index. Add 2 or more filters on indexed fields and preview the result - the above error message will be shown.

Proposed resolution

Attached patch concatenates multiple filters into the filters option, to generate valid syntax.