Add license metadata for std dependencies

These five crates are in the dependency tree of `std` but lack license metadata:
- `alloc`
- `core`
- `panic_abort`
- `panic_unwind`
- `unwind`

Querying the dependency tree of `std` is a useful thing to be able to do, since these crates will typically be linked into Rust binaries. Tools show the license fields missing, as seen in rust-lang#67014 (comment). This PR adds the license field for the five crates, based on the license of the `std` package and this repo as a whole. I also added the `repository` and `descriptions` fields, since those seem useful. For `description`, I copied text from top-level comments for the respective modules - except for `unwind` which has none.

I also note that rust-lang#73530 attempted to add license metadata for all crates in this repo, but was rejected because there was question about some of them. I hope that this smaller change, focusing only on the runtime dependencies, will be easier to review.

cc `@Mark-Simulacrum` `@Lokathor`

Add license metadata for std dependencies

These five crates are in the dependency tree of `std` but lack license metadata:
- `alloc`
- `core`
- `panic_abort`
- `panic_unwind`
- `unwind`

Querying the dependency tree of `std` is a useful thing to be able to do, since these crates will typically be linked into Rust binaries. Tools show the license fields missing, as seen in rust-lang#67014 (comment). This PR adds the license field for the five crates, based on the license of the `std` package and this repo as a whole. I also added the `repository` and `descriptions` fields, since those seem useful. For `description`, I copied text from top-level comments for the respective modules - except for `unwind` which has none.

I also note that rust-lang#73530 attempted to add license metadata for all crates in this repo, but was rejected because there was question about some of them. I hope that this smaller change, focusing only on the runtime dependencies, will be easier to review.

cc ``@Mark-Simulacrum`` ``@Lokathor``

Add license metadata for std dependencies

These five crates are in the dependency tree of `std` but lack license metadata:
- `alloc`
- `core`
- `panic_abort`
- `panic_unwind`
- `unwind`

Querying the dependency tree of `std` is a useful thing to be able to do, since these crates will typically be linked into Rust binaries. Tools show the license fields missing, as seen in rust-lang#67014 (comment). This PR adds the license field for the five crates, based on the license of the `std` package and this repo as a whole. I also added the `repository` and `descriptions` fields, since those seem useful. For `description`, I copied text from top-level comments for the respective modules - except for `unwind` which has none.

I also note that rust-lang#73530 attempted to add license metadata for all crates in this repo, but was rejected because there was question about some of them. I hope that this smaller change, focusing only on the runtime dependencies, will be easier to review.

cc ```@Mark-Simulacrum``` ```@Lokathor```

Rollup of 7 pull requests

Successful merges:

 - rust-lang#82374 (Add license metadata for std dependencies)
 - rust-lang#82683 (Document panicking cases for integer division and remainder)
 - rust-lang#83272 (Clarify non-exact length in the Iterator::take documentation)
 - rust-lang#83338 (Fix test for rust-lang#82270)
 - rust-lang#83351 (post-drop-elab check-const: explain why we still check qualifs)
 - rust-lang#83367 (Improve error message for unassigned query provider)
 - rust-lang#83372 (SplitInclusive is public API)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup