fix: unhide tokens with low occurrences for some chains

[maxime-oe]

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
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Narrow change to token visibility on one chain’s spam heuristic; no auth, persistence, or API contract changes.

Overview
EVM ERC-20 spam filtering in TokenDataSource now uses a per-chain minimum aggregator occurrence instead of a single global threshold of 3 for every chain.

A new MIN_TOKEN_OCCURRENCES_PER_CHAIN_OVERRIDE map sets eip155:5042 (Arc) to 1, because the chain is not fully released yet and legitimate tokens (e.g. EURC) can report fewer aggregator hits. Other chains still use MIN_TOKEN_OCCURRENCES (3). Custom-import bypass and the MUSD allowlist are unchanged; only the comparison uses minOccurrences from the override or default.

evmErc20Ids is typed as Caip19AssetId[] for consistency with parseCaipAssetType.

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