fix(doctor): improve target and sdk compatibility detection on <8.2

[edusperoni]

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• Tests for the changes are included.

What is the current behavior?

Building with build-tools 31 or 32 on @nativescript/android < 8.2 fails.

What is the new behavior?

Building on < 8.2 now tries to use a supported targetSdk, compileSdk and buildToolsVersion, or otherwise fails with a message indicating the issue (missing build-tools in the correct range).