result: fix wrong implied lifetime in col_specs()

As `ColumnSpec` is now parametrised by a lifetime, methods that return
it implicitly bound its lifetime with lifetime of `&self`. This bug
would lead to inefficiencies.
As a fix, an explicit lifetime is added in every method returning
`ColumnSpec`.

scylla-cql/src/frame/response/result.rs

@@ -549,7 +549,7 @@ impl<'a> ResultMetadata<'a> {
     }
 
     #[inline]
-    pub fn col_specs(&self) -> &[ColumnSpec] {
+    pub fn col_specs(&self) -> &[ColumnSpec<'a>] {
         &self.col_specs
     }
 }

scylla/src/transport/iterator.rs

@@ -396,7 +396,7 @@ impl RowIterator {
     }
 
     /// Returns specification of row columns
-    pub fn get_column_specs(&self) -> &[ColumnSpec] {
+    pub fn get_column_specs(&self) -> &[ColumnSpec<'static>] {
         self.current_page.metadata.col_specs()
     }
 

scylla/src/transport/query_result.rs

@@ -138,7 +138,7 @@ impl QueryResult {
 
     /// Returns column specifications.
     #[inline]
-    pub fn col_specs(&self) -> &[ColumnSpec] {
+    pub fn col_specs(&self) -> &[ColumnSpec<'static>] {
         self.metadata
             .as_ref()
             .map(|metadata| metadata.col_specs())
@@ -147,7 +147,7 @@ impl QueryResult {
 
     /// Returns a column specification for a column with given name, or None if not found
     #[inline]
-    pub fn get_column_spec<'a>(&'a self, name: &str) -> Option<(usize, &'a ColumnSpec)> {
+    pub fn get_column_spec<'a>(&'a self, name: &str) -> Option<(usize, &'a ColumnSpec<'static>)> {
         self.col_specs()
             .iter()
             .enumerate()