Add strict FT/NFT metadata flag

[rafaelcr]

We currently have flags that enable FT/NFT metadata processing in .env, but this does not guarantee the metadata is available when required.
We should add another flag that toggles a strict mode (STACKS_API_METADATA_STRICT_MODE) that, when enabled, it will try again forever if the metadata retrieval error is recoverable. If it's not, then try a given number of times before failing.

Relevant codepaths:

stacks-blockchain-api/src/event-stream/tokens-contract-handler.ts

Line 629 in f29919b

logger.warn(

stacks-blockchain-api/src/event-stream/tokens-contract-handler.ts

Line 645 in f29919b

logger.warn(

[MHassanTariq]

@rafaelcr can you tell me how can I reproduce this error? And how to check if the metadata retrieval error is recoverable?

[rafaelcr]

When I filed this issue we didn't have a specific error in mind. Recoverable errors would be timeouts, parsing errors, etc. that could be affected by network performance or some other code paths. Critical errors would be 500 error codes and things like that. @MHassanTariq