Rollup merge of #99027 - tmiasko:basic-blocks, r=oli-obk

Replace `Body::basic_blocks()` with field access

Since the refactoring in #98930, it is possible to borrow the basic blocks
independently from other parts of MIR by accessing the `basic_blocks` field
directly.

Replace unnecessary `Body::basic_blocks()` method with a direct field access,
which has an additional benefit of borrowing the basic blocks only.

compiler/rustc_mir_transform/src/coverage/mod.rs

@@ -80,7 +80,7 @@ impl<'tcx> MirPass<'tcx> for InstrumentCoverage {
             return;
         }
 
-        match mir_body.basic_blocks()[mir::START_BLOCK].terminator().kind {
+        match mir_body.basic_blocks[mir::START_BLOCK].terminator().kind {
             TerminatorKind::Unreachable => {
                 trace!("InstrumentCoverage skipped for unreachable `START_BLOCK`");
                 return;