Fix clippy::needless_borrow in the compiler

[Nilstrieb]

x clippy compiler -Aclippy::all -Wclippy::needless_borrow --fix.

Then I had to remove a few unnecessary parens and muts that were exposed now.

r? @compiler-errors you told me you want to review this

I will do a self review first (which, for this, is easiest on GitHub once the PR is open) - did it

[Nilstrieb]

there will probably quite some of those - I will not fix them here

[rustbot]

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

Some changes occurred in rustc_ty_utils::consts.rs

cc @BoxyUwU

Some changes might have occurred in exhaustiveness checking

cc @Nadrieril

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

This PR changes Stable MIR

cc @oli-obk, @celinval, @spastorino, @ouz-a

Some changes occurred in engine.rs, potentially modifying the public API of ObligationCtxt.

cc @lcnr, @compiler-errors

Some changes occurred in need_type_info.rs

cc @lcnr

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[Nilstrieb]

good to go!

[compiler-errors]

I verified this by reproducing the command above and comparing the output.

@bors r+ p=10

[bors]

📌 Commit 21a8705 has been approved by compiler-errors

It is now in the queue for this repository.

[bors]

⌛ Testing commit 21a8705 with merge fec80b4...

[bors]

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing fec80b4 to master...

[rust-timer]

Finished benchmarking commit (fec80b4): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.8%	[0.8%, 0.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-0.6%, -0.6%]	1
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 679.348s -> 675.654s (-0.54%)
Artifact size: 313.77 MiB -> 313.77 MiB (0.00%)