Introduce a setting to skip using ignoredSource

[salvatore-campagna]

Description

IgnoredSource uses special logic to handle ignored values and encodes them at indexing time to later be able to return reconstructed source including ignored field values. We experienced some issues with it, affecting the decoding logic, and decided to introduce a mechanism that allows us to disable its usage. We need to do that both at index and query time. This setting is meant to be used as a "last-resourt" option to deal with possible issues affecting document indexing or queries.

The default behavior should be such that ignoredSource is used both at indexing time and query time. Not using the field at indexing or query time should be possible by changing the setting value.

Issues have been observer in clusters running version 8.15.0 and 8.15.1. As a result we need to make sure the bug fix is backported to 8.15.2.

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)