Chat: display failure text and restructure

[rmackay9]

This includes a few unrelated changes:

1. Chat window's status update displays a detailed "human readable" reason for Assistant failures. Eg. when usage limits are reached we receive this long message, "failed: Rate limit reached for gpt-4-1106-preview in organization org-fA312A0gDmmQRCAgojIFOi9G on tokens_usage_based per day: Limit 500000, Used 497355, Requested 4096. Please try again in 4m10.732s. Visit https://platform.openai.com/account/rate-limits to learn more." We could display a shorter "code" which would be just, "rate_limit_reached" but for now we display the full message
2. Chat's function calls made consistent and redundant code removed by using getattr()
3. Assistant Instructions improved for CONDITION_YAW to reduce mix-ups between relative and absolute angles
4. Set-position-target-global-int simplifies function's "type_mask" field explanation simplified to improve chance that assistant picks the correct value

This has been tested in SITL.