fix(pid_longitudinal_controller): revive hysteresis of state transition

[takayuki5168]

Description

Previously, there was a hysteresis between drive_state_stop_dist and stopping_state_stop_dist so that the state transition of DRIVE <--> STOPPED will not chatter.

However, the following commit removed the hysteresis by mistake, so this PR revived it.
c6a3df8#diff-a311c12a65b491b5b4c0e9e5ee83bc1488a360826fe46e4204355c9fe009127eL14

Tests performed

unit test

Effects on system behavior

No chattering of the DRIVE/STOPPED state transition in pid_longitudinal_controller

Interface changes

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[kosuke55]

better to comment why 0.49

[takayuki5168]

@kosuke55
Let me know if the description is unclear. I added a hysteresis 0.1 to stopping_state_stop_dist.

[kosuke55]

I meant comment in param file.
but it is ok because I can find this PR