Add try priors as finally lock label andecedents rather than pre finally label antecedents

[weswigham]

Fixes #29684

Rather than

                (1-pre-try-flow) <--(inner try flows) <-- (2-post-try-flow)
                 ^                           ^^^^              ^
                 |*****(3-pre-finally-label) ------------------|
                               ^
                               |-- ... <-- (4-post-finally-label) <--- (5)

now we

                (1-pre-try-flow) <--(inner try flows) <-- (2-post-try-flow)
                 ^                           ^^^^              ^
                 |-----(pre-finally-flow)-------|              |
                            ^                                  |
                            |*****(3-pre-finally-label)--------|
                                       ^
                                       |-- ... <-- (4-post-finally-label) <--- (5)

so all the inner try flows are behind the lock.

[DanielRosenwasser]

It'd also be awesome if you could add the comment in this PR to the code ;)