Allow expected content-type to ignore parameters (#3724)

Fixes: #3471

## Motivation and Context
An issue was raised about a mobile client that appends "; charset=utf-8"
to the Content-Type when using restJson1. The [latest
RFC](https://www.rfc-editor.org/rfc/rfc8259) for "application/json" does
not register a charset parameter, but indicates it is reasonable to
accept it.

## Description
This change loosens the validation of the expected content type to allow
all parameters.

## Testing
* Tests for each protocol were added to
[smithy](https://github.com/smithy-lang/smithy/pull/2296)
* ran the runtime and codegen tests
* Added test for rest-xml, as smithy-rs does not currently run the
smithy tests.

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

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