Warn character truncation once only

[Adaickalavan]

• Character truncation warning message from observation space formatter tends to fill up the terminal. Example:

  WARNING:smarts.env.utils.observation_conversion:`vehicle id` named `car-flow-route-E1_2_0-E3_2_max--5782264158901839037--6390006830799584855--3-0.2` is more than `50` characters long. It will be truncated and may cause unintended issues with navigation and lane identification.
  WARNING:smarts.env.utils.observation_conversion:`vehicle id` named `car-flow-route-E1_0_0-E3_0_max-6963017027078397547--6390006830799584855--0-0.2` is more than `50` characters long. It will be truncated and may cause unintended issues with navigation and lane identification.
  WARNING:smarts.env.utils.observation_conversion:`vehicle id` named `car-flow-route-E1_0_0-E3_0_max-6963017027078397547--6390006830799584855--0-0.3` is more than `50` characters long. It will be truncated and may cause unintended issues with navigation and lane identification.
  WARNING:smarts.env.utils.observation_conversion:`vehicle id` named `car-flow-route-E1_2_0-E3_2_max--5782264158901839037--6390006830799584855--3-0.2` is more than `50` characters long. It will be truncated and may cause unintended issues with navigation and lane identification.

• Hence, warn only on the first occurence.
• Is there better a way to warn once only?

[Gamenot]

This seems like an important warning message. I am biased towards saying that this should be an error.

[Gamenot]

My only thought for resolving this is to shorten the id or add configuration to increase the character limit.

[Adaickalavan]

This seems like an important warning message. I am biased towards saying that this should be an error.

• If this warning is converted into an error, then the simulation might not proceed far as this warning currently pops up very frequently.
• The character truncation only affects the formatted observations returned to the users model, whereas smarts internally still has access to and may use the full untruncated vehicle ids.

[Gamenot]

...

• If this warning is converted into an error, then the simulation might not proceed far as this warning currently pops up very frequently.

That is fair, if they want the full observations they would then be forced to use SMARTS observation object directly.

• The character truncation only affects the formatted observations returned to the users model, whereas smarts internally still has access to and may use the full untruncated vehicle ids.

Then I think we should shorten the generated id length. I am going to put up a PR for it.