Avoid spurious backtrace / log message on critical error

[daverigby]

Problem

On a critical error (e.g. existing index and --overwrite not specified), VSB prints a large amount of spurious / unnecessary output - e.g:

vsb --database=pinecone --pinecone_api_key=XXX
    --workload=synthetic-proportional \
    --synthetic_records=1000 --synthetic_requests=100 \
    --synthetic_insert_ratio=0.3 --synthetic_query_ratio=0.5 \
    --synthetic_delete_ratio=0.1 --synthetic_update_ratio=0.1 \
    --synthetic_dimensions=768 --synthetic_query_distribution=zipfian \
    --synthetic_metadata=id:10n --synthetic_metadata=tags:5s10l \
    --pinecone_index_name=daver-synthetic-test
2025-01-10T14:44:11 INFO     Vector Search Bench: Starting experiment with backend='pinecone', workload='synthetic-proportional', users=1, requests_per_sec=unlimited
...
2025-01-10T14:44:12 CRITICAL PineconeDB: Index 'daver-synthetic-test' already exists - cowardly refusing to overwrite existing data. Specify --overwrite to delete it, or specify --skip-populate to skip population phase.
Traceback (most recent call last):
  File "/Users/dave/repos/pinecone-io/VSB/vsb/users.py", line 64, in setup
    self.database.initialize_population()
  File "/Users/dave/repos/pinecone-io/VSB/vsb/databases/pinecone/pinecone.py", line 155, in initialize_population
    raise StopUser()
locust.exception.StopUser
Performing Setup phase                         0/? ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━  0:00:00   %

This causes the "CRITICAL" message to get somewhat lost.

Solution

Modify the handling of critical errors to use an explicit DoneFailed state in the state machine, which handles the shutdown without adding backtraces, also also updating messages to be more applicable to a failed run:

2025-01-10T14:47:20 INFO     Vector Search Bench: Starting experiment with backend='pinecone', workload='synthetic-proportional', users=1, requests_per_sec=unlimited
...
2025-01-10T14:47:22 CRITICAL PineconeDB: Index 'daver-synthetic-test' already exists - cowardly refusing to overwrite existing data. Specify --overwrite to delete it, or specify --skip-populate to skip population phase.
✘ Setup cancelled                              1/1 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 0:00:00 00:00 ~

Type of Change

• Bug fix (non-breaking change which fixes an issue)