Backport to 1.46.x: priority and ring_hash LBs: fix interactions when using ring_hash under priority (#29332)

[yashykt]

…er priority (#29332)

• refactor connection delay injection from client_lb_end2end_test

• fix build

• fix build on older compilers

• clang-format

• buildifier

• a bit of code cleanup

• start failover time whenever the child reports CONNECTING, and don't cancel when deactivating

• clang-format

• rewrite test

• simplify logic in priority policy

• clang-format

• switch to using a bit to indicate child healthiness

• fix reversed comment

• more changes in priority and ring_hash.

priority:

• go back to starting failover timer upon CONNECTING, but only if seen
  READY or IDLE more recently than TRANSIENT_FAILURE

ring_hash:

• don't flap back and forth between IDLE and CONNECTING; once we go
  CONNECTING, we stay there until either TF or READY
• after the first subchannel goes TF, we proactively start another
  subchannel connecting, just like we do after a second subchannel
  reports TF, to ensure that we don't stay in CONNECTING indefinitely if
  we aren't getting any new picks
• always return ring hash's picker, regardless of connectivity state
• update the subchannel connectivity state seen by the picker upon
  subchannel list creation
• start proactive subchannel connection attempt upon subchannel list
  creation if needed

• ring_hash: fix connectivity state seen by aggregation and picker

• fix obiwan error

• swap the order of ring_hash aggregation rules 3 and 4

• restore original test

• refactor connection injector QueuedAttempt code

• add test showing that ring_hash will continue connecting without picks

• clang-format

• don't actually need seen_failure_since_ready_ anymore

• fix TSAN problem

• address code review comments