This fixes some problems wrt dependence of captures in lambdas with
an explicit object parameter.
[temp.dep.expr] states that
> An id-expression is type-dependent if [...] its terminal name is
> - associated by name lookup with an entity captured by copy
> ([expr.prim.lambda.capture]) in a lambda-expression that has
> an explicit object parameter whose type is dependent [dcl.fct].
There were several issues with our implementation of this:
1. we were treating by-reference captures as dependent rather than
by-value captures;
2. tree transform wasn't checking whether referring to such a
by-value capture should make a DRE dependent;
3. when checking whether a DRE refers to such a by-value capture, we
were only looking at the immediately enclosing lambda, and not
at any parent lambdas;
4. we also forgot to check for implicit by-value captures;
5. lastly, we were attempting to determine whether a lambda has an
explicit object parameter by checking the `LambdaScopeInfo`'s
`ExplicitObjectParameter`, but it seems that that simply wasn't
set (yet) by the time we got to the check.
All of these should be fixed now.
This fixes#70604, #79754, #84163, #84425, #86054, #86398, and #86399.
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