feat: add min spec guard panel at load

[davidejensen]

Pull Request Description

What does this PR change?

Fix #2887
This PR implements a screen shown at start time that notifies the user they don't have met the minimum hardward requirements to run DCL, it still lets them play.

Test Instructions

Test Steps

First test:

1. Launch the build with a computer that has more than the minimum hardware requirements
2. Verify that it loads fine

Second test:

1. Launch the build with a computer that has less than the minimum hardware requirements, if you don't have one you can launch the build via terminal with the parameter --forceMinimumSpecsScreen to simulate it
2. Verify that during the initial loading a screen appears stating the minimum requirements
3. Verify that all the buttons work as expected

[github-actions]

Windows and Mac build successful in Unity Cloud! You can find a link to the downloadable artifact below.

Name	Link
Commit	2f03257
Logs	https://github.com/decentraland/unity-explorer/actions/runs/14400051560
Download Windows	https://github.com/decentraland/unity-explorer/suites/37033126934/artifacts/2926429981
Download Windows S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/feat/min-spec-warning/pr-8622-2f03257/Decentraland_windows64.zip
Download Mac	https://github.com/decentraland/unity-explorer/suites/37033126934/artifacts/2926432157
Download Mac S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/feat/min-spec-warning/pr-8622-2f03257/Decentraland_macos.zip
Built on	2025-04-11T09:56:37Z

[DafGreco]

✔️ PR reviewed and approved by QA on both platforms following instructions playing both happy and un-happy path

Regressions for this ticket had been performed in order to verify that the normal flow is working as expected:

• ✔️ Backpack and wearables in world
• ✔️ Emotes in world and in backpack
• ✔️ Teleport with map/coordinates/Jump In
• ✔️ Profile card
• ✔️ Camera
• ✔️ Skybox
• ✔️ Settings

[lorenzo-ranciaffi]

LGTM!
Only a small issue for the failing test