chore: bump BFD toggle wait timeout (sonic-net#15939)

Description of PR
Bump the BFD toggle wait timeout to 450 seconds to give BFD session enough time to go up/down.

Summary:
Fixes # (issue) Microsoft ADO 30112171

Approach
What is the motivation for this PR?
We noticed that 300 seconds is not enough for BFD session to go up/down, so Cisco suggested us to bump it to 450 seconds.

tests/bfd/bfd_helpers.py

@@ -32,7 +32,7 @@ def prepare_bfd_state(dut, flag, expected_bfd_state):
 def verify_bfd_only(dut, nexthops, asic, expected_bfd_state):
     logger.info("BFD verifications")
     assert wait_until(
-        300,
+        450,
         10,
         0,
         lambda: verify_bfd_state(dut, nexthops.values(), asic, expected_bfd_state),
@@ -715,7 +715,7 @@ def verify_given_bfd_state(asic_next_hops, port_channel, asic_index, dut, expect
 
 def wait_until_given_bfd_down(next_hops, port_channel, asic_index, dut):
     assert wait_until(
-        300,
+        450,
         10,
         0,
         lambda: verify_given_bfd_state(next_hops, port_channel, asic_index, dut, "Down"),