clippy: core lints

[brooksprumo]

Problem

There are new nightly clippy lints in the core crate. Refer to #34626 for more information.

warning: writing `&Vec` instead of `&[_]` involves a new object where a slice will do
   --> core/src/banking_stage/consumer.rs:153:29
    |
153 |         packets_to_process: &Vec<Arc<ImmutableDeserializedPacket>>,
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: change this to: `&[Arc<ImmutableDeserializedPacket>]`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_arg
    = note: `#[warn(clippy::ptr_arg)]` on by default

warning: `solana-core` (lib) generated 1 warning

warning: unit tests in doctest are not executed
  --> core/tests/fork-selection.rs:15:5
   |
15 |   //! #[test]
   |  _____^
16 | | //! #[ignore]
17 | | //! fn test_all_partitions() {
   | |__________________________^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#test_attr_in_doctest
   = note: `#[warn(clippy::test_attr_in_doctest)]` on by default

warning: `solana-core` (test "fork-selection") generated 1 warning

Summary of Changes

Fix 'em.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (09a94b8) 81.8% compared to head (383401d) 81.8%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #34629   +/-   ##
=======================================
  Coverage    81.8%    81.8%           
=======================================
  Files         824      824           
  Lines      222260   222261    +1     
=======================================
+ Hits       181893   181896    +3     
+ Misses      40367    40365    -2