Stop using --legacy

[marcelofabri]

https://developer.apple.com/documentation/xcode-release-notes/xcode-16_3-release-notes#Deprecations mentions:

Some parts of xcresulttool API are deprecated and will be removed in the future. Upon removal they can be used with --legacy flag provided. Please use the new commands from above instead. List of deprecated commands:

xcresulttool get [object] --legacy --path <path> [--id <id>] [--version <version>] [--format <format>]
xcresulttool export [object] --legacy --path <path> --output-path <output-path> [--id <id>] --type <type> [--version <version>]
xcresulttool graph --legacy --path <path> [--id <id>] [--version <version>]

We should look into using the suggested commands on Xcode 16+ to avoid breaking changes when Apple decides to remove the --legacy flag.

[shahidlatif2021]

any update on this?

[aaronsky]

Based on some quick experimentation, it seems like this will have to happen if this library is to ever support swift-testing results