feat(webpack): add support for 'projectName' config on Xcode build files

[apburgess]

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• 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 - https://github.com/NativeScript/NativeScript/blob/master/tools/notes/WritingUnitTests.md.

What is the current behavior?

Currently Xcode build files are generated using the basename of the project directory.

What is the new behavior?

If (and only if) the new 'projectName' setting is present in nativescript.config.ts, the Xcode build files are generated using this name instead of the basename.

Fixes/Implements/Closes NativeScript/nativescript-cli#2107

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[apburgess]

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[apburgess]

Linked to PRs NativeScript/nativescript-cli#5801 and NativeScript/docs#143.