Etherscan Plugin: remove 34 key length rule, replace deprecated block explorer APIs

[kartojal]

Rationale

Lately Avalanche and Boba networks replaced their block explorer to Routescan based explorers. This PR changes the block explorer URL to allow Remix devs to verify in Avalanche, Boba, Chiliz and Metis block explorers.

Changes

• Remove API KEY 34 length rule, due other block explorers may not require an API KEY or their API KEY length may be different.
• Replace Avalanche and Boba block explorer API URLs to the currently maintained ones, both testnet and production.
• Add Chiliz and Metis block explorer API URLs, both testnet and production

Proposal block explorers to add

Network	ChainId	Block Explorer Provider	API URL
Avalanche Mainnet	43114	Routescan	https://api.routescan.io/v2/network/mainnet/evm/43114/etherscan
Avalanche Fuji Testnet	43113	Routescan	https://api.routescan.io/v2/network/testnet/evm/43113/etherscan
Boba Mainnet	288	Routescan	https://api.routescan.io/v2/network/mainnet/evm/288/etherscan
Boba Testnet	2888	Routescan	https://api.routescan.io/v2/network/testnet/evm/2888/etherscan
Metis Andromenda Mainnet	1088	Routescan	https://api.routescan.io/v2/network/mainnet/evm/1088/etherscan
Metis Sepolia Testnet	59901	Blockscout	https://sepolia.explorer.metisdevops.link/api
Chiliz Mainnet	88888	Routescan	https://api.routescan.io/v2/network/mainnet/evm/88888/etherscan
Chiliz Spicy Testnet	88882	Routescan	https://api.routescan.io/v2/network/testnet/evm/88882/etherscan

[netlify]

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