Fix DiagnoseStaticExclusivity for lifetime dependent sub-objects

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For example:

struct InoutPair: ~Escapable, ~Copyable {
  @_lifetime(self: &x)
  mutating func insertX(_ x: inout Int) {...}

  @_lifetime(self: &y)
  mutating func insertY(_ y: inout Int) {...}
}

struct Pair {
  var x: Int
  var y: Int

  mutating func run() {
    var inoutPair = InoutPair()
    inoutPair.insertX(&x)
    inoutPair.insertY(&y)

    take(inoutPair) // The access of both &x and &y are extended up to here
  }
}

In the Pair.run method, the accesses to &x and &y are overlapping because the
final value of inoutPair depends on both. Fix DiagnoseStaticExclusivity to
recognize that these accesses are to independent subobjects even though that
have a lifetime dependency.

Fixes rdar://175271283 ([exclusivity] handle simultaneous sub-object exclusivity
with lifetime dependencies)

We can consider a more robust design in the future:
rdar://175275018 ([nonescapable] create mark_dependence on the projection rather than the base)

But in the meantime, this problem basically makes it impossible to have dependencies on multiple sub-objects.

[atrick]

@swift-ci test

[atrick]

I tagged a bunch of potential reviewers here because it's an easy one-line fix and I'm not sure who has time to look at it.

[atrick]

@swift-ci test