statement: remove per-statement custom timestamp setting

A timestamp is something related to a single execution of a statement,
not to the statement itself. Also, setting a timestamp on a statement
inside the Batch would not set a timestamp on a Batch itself, which has
shown to be a pitfall.
This commit finishes the migration to the new per-execution timestamp
API by removing timestamp settings from statements.

scylla/src/statement/batch.rs

@@ -109,18 +109,6 @@ impl Batch {
         self.config.tracing
     }
 
-    /// Sets the default timestamp for this batch in microseconds.
-    /// If not None, it will replace the server side assigned timestamp as default timestamp for
-    /// all the statements contained in the batch.
-    pub fn set_timestamp(&mut self, timestamp: Option<i64>) {
-        self.config.timestamp = timestamp
-    }
-
-    /// Gets the default timestamp for this batch in microseconds.
-    pub fn get_timestamp(&self) -> Option<i64> {
-        self.config.timestamp
-    }
-
     /// Set the retry policy for this batch, overriding the one from execution profile if not None.
     #[inline]
     pub fn set_retry_policy(&mut self, retry_policy: Option<Arc<dyn RetryPolicy>>) {

scylla/src/statement/mod.rs

@@ -33,7 +33,6 @@ pub(crate) struct StatementConfig {
 
     pub(crate) skip_result_metadata: bool,
     pub(crate) tracing: bool,
-    pub(crate) timestamp: Option<i64>,
     pub(crate) request_timeout: Option<Duration>,
 
     pub(crate) history_listener: Option<Arc<dyn HistoryListener>>,

scylla/src/statement/prepared_statement.rs

@@ -370,19 +370,6 @@ impl PreparedStatement {
         self.config.skip_result_metadata
     }
 
-    /// Sets the default timestamp for this statement in microseconds.
-    /// If not None, it will replace the server side assigned timestamp as default timestamp
-    /// If a statement contains a `USING TIMESTAMP` clause, calling this method won't change
-    /// anything
-    pub fn set_timestamp(&mut self, timestamp: Option<i64>) {
-        self.config.timestamp = timestamp
-    }
-
-    /// Gets the default timestamp for this statement in microseconds.
-    pub fn get_timestamp(&self) -> Option<i64> {
-        self.config.timestamp
-    }
-
     /// Sets the client-side timeout for this statement.
     /// If not None, the driver will stop waiting for the request
     /// to finish after `timeout` passed.

scylla/src/statement/query.rs

@@ -103,19 +103,6 @@ impl Query {
         self.config.tracing
     }
 
-    /// Sets the default timestamp for this statement in microseconds.
-    /// If not None, it will replace the server side assigned timestamp as default timestamp
-    /// If a statement contains a `USING TIMESTAMP` clause, calling this method won't change
-    /// anything
-    pub fn set_timestamp(&mut self, timestamp: Option<i64>) {
-        self.config.timestamp = timestamp
-    }
-
-    /// Gets the default timestamp for this statement in microseconds.
-    pub fn get_timestamp(&self) -> Option<i64> {
-        self.config.timestamp
-    }
-
     /// Sets the client-side timeout for this statement.
     /// If not None, the driver will stop waiting for the request
     /// to finish after `timeout` passed.