Getting rid of the legacy JS integration in favor of JSI with V8 impl…

[mganandraj]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

With this change, i'm trying to cleanup a lot of differences that we've managed to accumulate over the last couple of years in JS engine integration. Specifically, we had our own implementation of JSEExecutor interface called V8Executor (Just like CHakraExecutor on Win32/UWP). And we used to switch between V8Executor and JSCExecutor. The switch and the V8Executor remained even though JSCExecutor already went away, which made the switch useless, but most of the code remained which clutterd our build scripts.

With this change, i originally intented to remove the switch and cleanup the build scripts. But, in the process, it felt a lot more efficient to get rid of the V8Executor and switch to JSI engines altogether, as the FB repo (even v0.60.0) has only JSI based executors now. It'd be a backward step to even keep the V8Executor around.

Hence, with this change, we take a big stride forward, by switching to V8 based JSI runtime exclusively. I've already tested RNTester, Modern commenting and LPC already.

This change may a bit aggressive, but i think this will help us a lot in the long time with maintainabiltiy and even performance. Now that we are going to switch to JSI runtimes in Windows very soon, this change will help us to unify the JSI implementation across platforms.

There is a small change in Office code required which i'll send a CR for androidxupgrade override.

Focus areas to test

SDX functionalities.

Microsoft Reviewers: Open in CodeFlow

[pull-bot]

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[BarinderGrewal]