Capability checking does not respect name shadowing

[byorgey]

Describe the bug
If a lambda happens to shadow a name which is already defined, everything works as it should except that capability checking will attribute the capabilities needed for the existing definition to any uses of the name inside the lambda, even though those uses of the name should refer to the lambda binder, which shadows the existing definition.

To reproduce
Start a new classic mode game. Then type at the REPL:

def foo : int = 1 + 2 end
def bar : dir -> cmd () = \foo. turn foo end
build {bar left}

You will get an error like build: this would require installing devices you don't have: lambda and calculator.

Expected behavior
Getting an error about lambda is expected. However, the error about calculator is unexpected, since the definition of bar neither directly nor indirectly uses any arithmetic. In particular it does not refer to foo : int.

Additional context
I checked and #373 still has the same issue, it just formats the error message differently. This is expected since the error probably has to do with the capability checker, which #373 did not change.

Marking this as 'Critical' since if you run into this it is very mysterious and hard to figure out what is wrong. It could also completely block you in a situation where you should have the proper devices but the system is telling you that you don't. I ran into this during a playthrough and was completely stumped for a little while.

[byorgey]

A similar issue arises with let, e.g.

def foo : int = 1 + 2 end
def bar = let foo = left in turn foo end
build {bar}

leads to an error about dictionary and calculator.

[byorgey]

And one more, given the same definition of foo:

def bar3 = foo <- grab; give base foo end
build {bar3}

also gives an error about calculator.