Motivation:

Swift 6.1 has been released, we should add it to our CI coverage.

Modifications:

Add additional Swift 6.1 jobs where appropriate in main.yml,
pull_request.yml

Result:

Improved test coverage.

Motivation:

Swift 5.9 is no longer supported, we should bump the tools version and
remove it from our CI.

Modifications:

* Bump the Swift tools version to Swift 5.10
* Remove Swift 5.9 jobs where appropriate in main.yml, pull_request.yml

Result:

Code reflects our support window.

### Motivation:

Some errors do not show up in debug builds. Enabling release mode builds
improves the CI coverage.

### Modifications:

Enable release mode builds for pull requests and scheduled builds on
main.

### Result:

Improved CI coverage.

### Motivation

This package wasn't building on Android, causing various dependent
packages to also fail to build.

### Modifications

Add the necessary `import(Android)` to successfully build.

### Result

The package can now be built for Android.

### Test Plan

~~Added CI to build and run against an Android emulator using
[swift-android-action](https://github.com/marketplace/actions/swift-android-action).~~