Create an instance from a mod pack

[Maximilian-Nesslauer]

Closes #366

• The pack page and each row on the Modpacks tab have a new "New instance from this pack" button.
• It opens the "Create instance" window with the pack name filled in. You can change the name. An empty or taken name shows an error, and the window stays open.
• Borea then installs the pack into the new instance, with the same progress, Stop, Pause, choices and task history as Add.
• When the pack has a warning, the row waits for your confirmation as before, and it names the instance that it will create.
• Borea creates the instance only when the pack can install. When nothing can install, or you stop before the install starts, no instance is created.
• When you stop or an install fails later, the instance stays with the mods that were installed, and the row says so.
• The new instance becomes the active instance when no instance is active. Otherwise the active instance stays.
• The instance page shows the pack and its version as the source of the new instance.
• An instance name that is taken now shows a translated error, also in the normal "New instance" window.
• Changing a choice while the row waits plans again, so the download size on the confirm button also follows for a pack that creates an instance.
• The CLI has borea pack install <pack> [version] --new-instance <name> in place of --instance. --dry-run shows the plan and creates nothing, and --json has the new fields newInstance, created and activated. instanceId is null when no instance was created.

Fixture output of borea pack install navigation-pack --new-instance Navigation, only the lines that the test checks:

Pack navigation-pack 1.0.0 into the new instance 'Navigation':
  installed  flight-tools 2.0.0  modpack
Created instance 'Navigation' (<id>). It is now the active instance.

[coveralls]

Coverage Report for CI Build 35498943046

Warning

Build has drifted: This PR's base is out of sync with its target branch, so coverage data may include unrelated changes.
Quick fix: rebase this PR. Learn more →

Coverage increased (+0.02%) to 87.349%

Details

• Coverage increased (+0.02%) from the base build.
• Patch coverage: 11 uncovered changes across 3 files (143 of 154 lines covered, 92.86%).
• 1 coverage regression across 1 file.

Uncovered Changes

File	Changed	Covered	%
src/Borea.App/ViewModels/MainViewModel.Packs.cs	61	52	85.25%
src/Borea.Cli/Commands/PackCommand.cs	55	54	98.18%
src/Borea.Storage/ModPacks/ModPackInstaller.cs	16	15	93.75%
Total (11 files)	154	143	92.86%

Coverage Regressions

1 previously-covered line in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
src/Borea.App/ViewModels/MainViewModel.Playtime.cs	1	68.06%

---

Coverage Stats

Relevant Lines:	26923
Covered Lines:	24537
Line Coverage:	91.14%
Relevant Branches:	13233
Covered Branches:	10539
Branch Coverage:	79.64%
Branches in Coverage %:	Yes
Coverage Strength:	6629.23 hits per line

---

💛 - Coveralls