This PR:

• Closes https://github.com/prisma/team-orm/issues/1327
• Deprecates feat(psl): GA fullTextIndex and fullTextSearch for provider = "mysql" #5031
• GAs fullTextSearch on mysql
• Introduces fullTextSearchPostgres for postgres, which replaces fullTextSearch
• Adapts existing tests, and introduces new ones

This is the first time we GA a preview feature for a a subset of every Prisma-supported connector, while also renaming a preview feature for a specific connector:

• we're only GA-ing fullTextSearch for provider = "mysql", but psl_core::common::preview_features::FeatureMap has no knowledge of which Prisma database provider is currently selected by the user
• we're renaming fullTextSearch as nativeFullTextSearchPostgres for provider = "postgresql" only

Hence, I've introduced psl_core::common::preview_features::FeatureMapWithProvider::<'a>, which, given a provider, exposes the same functionality as the old FeatureMap, but allows for escape hatches when provider = "mysql". FeatureMap is now a private struct.

I've added a default implementation of FeatureMapWithProvider as a convenience for https://github.com/prisma/language-tools, which is selected when the datasource block doesn't yet have a valid provider value.

The FeatureMap struct now has two new fields:

• native: BTreeMap<&'static str, PreviewFeatures>, which lists the valid connector-specific features. It's a map from database provider to the set of native preview features.
• renamed: BTreeMap<RenamedFeatureKey, RenamedFeatureValue>, which keeps track of the renamed deprecated issues. It's a map from a deprecated preview feature and an optional database provider to the new, active preview feature, along with information useful for diagnostic messages.

Both map entries are feature-gated at compile-time. Since BTreeMap insertion isn't const-initialisable, I had to move the FeatureMap instantiation into FeatureMapWithProvider::new, while also introducing std::sync::LazyLock for ALL_PREVIEW_FEATURES, the default FeatureMapWithProvider value.

• When on provider = "mysql", writing previewFeatures = ["fullTextSearch"] in schema.prisma now results in the following validation warning:

  Preview feature "fullTextSearch" is deprecated. The functionality can be used without specifying it as a preview feature.
  

• When on provider = "postgres" / provider = "postgresql", writing previewFeatures = ["fullTextSearch"] in schema.prisma now results in the following validation warning:

  On `provider = "postgresql"`, preview feature "fullTextSearch" has been renamed to "fullTextSearchPostgres". Learn more at https://pris.ly/d/fts-postgres.
  

• When on provider = "postgres" / provider = "postgresql", writing previewFeatures = ["fullTextSearchPostgres"] in schema.prisma is now valid.