This commit converts the index metadata of searchable snapshot indices using the `shared_cache`
storage type to:

- Remove all the `index.routing.allocation.(include|exclude|require)._tier` settings
- Sets `index.routing.allocation.include._tier_preference` to `data_frozen` automatically when the index metadata is read

This is in preperation to enforcing that the `_tier_preference` setting is always set to
`data_frozen` for shared cache SBIs.

Relates to elastic#70846, elastic#71013, elastic#70786, elastic#70141

…#71129)

This commit converts the index metadata of searchable snapshot indices using the `shared_cache`
storage type to:

- Remove all the `index.routing.allocation.(include|exclude|require)._tier` settings
- Sets `index.routing.allocation.include._tier_preference` to `data_frozen` automatically when the index metadata is read

This is in preperation to enforcing that the `_tier_preference` setting is always set to
`data_frozen` for shared cache SBIs.

Relates to #70846, #71013, #70786, #70141

We already set `data_frozen` for partial searchable snapshots when they are mounted (elastic#70786), and
automatically convert values other than the frozen role automatically for these snapshots when the
metadata is loaded (elastic#71014). This commit makes the `_tier_preference` setting validate that the
setting is *only* `data_frozen` when set on a partial searchable snapshot index.

…71155)

We already set `data_frozen` for partial searchable snapshots when they are mounted (#70786), and
automatically convert values other than the frozen role automatically for these snapshots when the
metadata is loaded (#71014). This commit makes the `_tier_preference` setting validate that the
setting is *only* `data_frozen` when set on a partial searchable snapshot index.

…lastic#71155)

We already set `data_frozen` for partial searchable snapshots when they are mounted (elastic#70786), and
automatically convert values other than the frozen role automatically for these snapshots when the
metadata is loaded (elastic#71014). This commit makes the `_tier_preference` setting validate that the
setting is *only* `data_frozen` when set on a partial searchable snapshot index.

…rence (#71155) (#71342)

* Enforce data_frozen for partial searchable snapshot _tier_preference (#71155)

We already set `data_frozen` for partial searchable snapshots when they are mounted (#70786), and
automatically convert values other than the frozen role automatically for these snapshots when the
metadata is loaded (#71014). This commit makes the `_tier_preference` setting validate that the
setting is *only* `data_frozen` when set on a partial searchable snapshot index.

* Handle mixed version clusters with pre-7.13.0 frozen SBIs

* Fix checkstyyyyyyyyle

* Pass index version in settings for test

* Unconditionally return only data_frozen for setting

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>