feat(ffi): Add IndexedDB and in-memory session stores support.

This patch introduces the `sqlite` and `indexeddb` feature flag,
enabling the use of SQLite or IndexedDB for the stores. This patch also
introduces the ability to use non-persistent, in-memory stores.

The new `ClientBuilder::in_memory_store`, `ClientBuilder::sqlite_store`
and `ClientBuilder::indexeddb_store` methods are introduced to
configure the stores. This patch adds new `SqliteStoreBuilder` and
`IndexedDbStoreBuilder` structure.

xtask/src/ci.rs

@@ -234,7 +234,7 @@ fn check_clippy() -> Result<()> {
         "rustup run {NIGHTLY} cargo clippy --workspace --all-targets
             --exclude matrix-sdk-crypto --exclude xtask
             --no-default-features
-            --features native-tls,sso-login,testing,experimental-element-recent-emojis
+            --features native-tls,sso-login,sqlite,testing,experimental-element-recent-emojis
             -- -D warnings"
     )
     .run()?;