Refactor QueryElevationComponent to prepare query subset matching

The goal is to prepare a second improvement to support query terms subset matching or query elevation rules.

Before that, we need to refactor the QueryElevationComponent. We make it extendible. We introduce the ElevationProvider interface which will be implemented later in a second patch to support subset matching. The current full-query match policy becomes a default simple MapElevationProvider.

• Add overridable methods to handle exceptions during the component initialization.
• Add overridable methods to provide the default values for config properties.
• No functional change beyond refactoring.
• Adapt unit test.