feat(multichain-account-service): populate maxConcurrency for BTC and TRX providers

[mathieuartu]

Explanation

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

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Note

Set default concurrency limit of 3 for Bitcoin and Tron account creation; update tests to cover default Infinity behavior and changelog.

• Providers:
  • Set maxConcurrency: 3 by default in BtcAccountProvider and TrxAccountProvider constructors.
• Tests:
  • Allow optional maxConcurrency in createTrackedProvider; conditionally include in config.
  • Add test asserting default maxConcurrency is Infinity when unspecified; verify throttling behavior remains correct.
• Changelog:
  • Note default limit of 3 concurrent account creations for Bitcoin and Tron providers under Unreleased.

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