Add release notes for Rust 1.63.0

[cuviper]

No description provided.

[rust-highfive]

r? @Mark-Simulacrum

(rust-highfive has picked a reviewer for you, use r? to override)

[cuviper]

This should be good as far as capturing noteworthy items, but suggestions are welcome in case I missed anything, especially for interesting "internal changes". I still need to tweak a lot of the wording and link stabilized APIs too.

cc @rust-lang/release

[joshtriplett]

I think the likely highlights for a blog post would be:

• I/O Safety, with a detailed explanation and some guidance about using it (e.g. using this instead of RawFd in libraries).
• explicit_generic_args_with_impl_trait (as a paragraph-sized note with one code example)
• The removal of migration mode in the borrow checker (as a brief mention with a link to the post at add nll-by-default blog post blog.rust-lang.org#989 , which we should merge before the release).

[tspiteri]

Nested [] break links.

[Mark-Simulacrum]

@bors r+ rollup p=1

[bors]

📌 Commit 99793d9 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit 99793d9 with merge 44bd81d...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 44bd81d to master...

[rust-timer]

Finished benchmarking commit (44bd81d): comparison url.

Instruction count

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: 😿 relevant regressions found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	1.3%	1.4%	6
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	N/A	N/A	0

Max RSS (memory usage)

Results

• Primary benchmarks: 😿 relevant regression found
• Secondary benchmarks: 🎉 relevant improvement found

	mean1	max	count2
Regressions 😿 (primary)	1.2%	1.2%	1
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-2.4%	-2.4%	1
All 😿🎉 (primary)	1.2%	1.2%	1

Cycles

Results

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: 😿 relevant regression found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	3.5%	3.5%	1
Improvements 🎉 (primary)	-3.4%	-3.4%	1
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	-3.4%	-3.4%	1

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³