Durable use cache: optimize env var existence checks

[mischnic]

We now separately track code that accesses non-inlined env vars at runtime in two categories

• (existing) actual reads, the full value is accessed
• (new) only unset/falsy/truthy is read at runtime

For the second case, we only need to invalidate use-cache functions when the given env var transitioned betwen unset/falsy/truthy. But transitioning between two different truthy values doesn't caused invalidation.

[mischnic]

• Durable use cache: fix runtime env var mutation #98558
• Durable use cache: optimize env var existence checks #98504 👈 (View in Graphite)
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[github-actions]

Tests Passed

Commit: 4068e2f

[lukesandberg]

we could defer this test to effect processing, this would be slightly more efficient since we would mostly not need to walk the AST path

[mischnic]

no, we can't. I first wanted to do it like this.

in the effect processing stage, we have [AstParentKind], which is only the type of the AST node, not the actual AST node. So here, we can only tell if this is anyFn(process.env.FOO) and not if it's actually Boolean(process.env.FOO)