Normalize URI paths during signing (except for S3) (#2018)

* De-dupe multiple leading forward slashes in request

This commit fixes a bug reported in
https://github.com/awslabs/aws-sdk-rust/issues/661.
Note that this de-duping is not part of URI path normalization because it
must happen to a request for any service, including S3.

* Normalize URI paths for canonical requests

This commit enables URI path normalization in aws-sigv4. It follows
https://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
to create the canonical URI that is part of the canonical request.

* Avoid using OS specific path separator

This commit updates the implementation of normalize_path_segment so that it
does not use an OS specific path separator, specifically "\\" on Windows and
always uses a forward slash "/". It addresses a test failure on Windows:
https://github.com/awslabs/smithy-rs/actions/runs/3518627877/jobs/5897764889.

* Fix the rustdoc::bare_urls warning from cargo doc

* Fix a typo Normalzie -> Normalize

* Limit de-duping multiple leading forward slashes to S3

This commit addresses https://github.com/awslabs/smithy-rs/pull/2018#issuecomment-1325283254.
There is a case  where an empty string between leading double forward
slashes is meaningful so blindly de-duping them breaks the use case.
Therefore, handling multiple leading forward slashes in this manner
should be applied only to S3.

* Add an integration test per https://github.com/awslabs/aws-sdk-rust/issues/661



This commit adds an integration test verifying the special rule for URI
path normalization applies to S3. That is, leading forward slashes should
be de-deduped and normalizing URI paths as prescribed in RFC 3986 should
be ignored.

* Update CHANGELOG.next.toml

* Revert 87b749c

This commit reverts 87b749c, the reason being that we need to better
understand the requirement for de-duplicating leading forward slashes
in requests, i.e. do we even need to do it or if so where should we
perform the de-dupe operation?

* Revert naming of UriPathNormalizationMode variants

This commit reverts the naming of variants in UriPathNormalizationMode.
They were PerRfc3986 and ForS3, but they should be more generic like
Enabled and Disabled as we had before.

* Update CHANGELOG.next.toml

* Simplify integration test using capture_request

This commit simplifies the integration test normalize-uri-path for s3.
Previously, the test used ReplayingConnection but it was an overkill
to test something as simple as whether the generated request contained
the expected URI and signature.

* Update aws/rust-runtime/aws-sigv4/src/http_request/settings.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-sigv4/src/http_request/settings.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-sigv4/src/http_request/uri_path_normalization.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Address review feedback on normalize_path_segment

This commit addresses the following code review feedback:
https://github.com/awslabs/smithy-rs/pull/2018#discussion_r1034192229
https://github.com/awslabs/smithy-rs/pull/2018#discussion_r1034194621
https://github.com/awslabs/smithy-rs/pull/2018#discussion_r1034195625

* Update CHANGELOG.next.toml

This commit addresses https://github.com/awslabs/smithy-rs/pull/2018#discussion_r1034198861

* Preallocate the Vec capacity for normalize_path_segment

This commit addresses https://github.com/awslabs/smithy-rs/pull/2018#discussion_r1034195625.
It counts the number of slashes to preallocate the capacity of a Vec used
in normalize_path_segment.

* Address https://github.com/awslabs/smithy-rs/pull/2018\#discussion_r1034188849



* Update aws/rust-runtime/aws-sigv4/src/http_request/settings.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-sigv4/src/http_request/settings.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

* Update aws/rust-runtime/aws-sigv4/src/http_request/settings.rs

Co-authored-by: John DiSanti <jdisanti@amazon.com>

Co-authored-by: Yuki Saito <awsaito@amazon.com>
Co-authored-by: John DiSanti <jdisanti@amazon.com>