client/container: ethereum-based: support Etherscan V2, add more L2 chains

- Implements support for unified API via Etherscan V2 (ethereum-based)
  * All ethereum-based L2s are now accessed via single API endpoint
    - Chains are now available via chain ID
  * Updates API key requirement for `fetch` ethereum-based subaccounts
    - The API key's value must now be prepended with "etherscan"
      * Previously was prepended per-chain ("ethereum" or "polygon")
    - The API key is now *required* (can be generated at etherscan.io)
      * Resolves fatal error in Etherscan::parse_response()
      * Impl will now handle if:
        - Config's API key/value is malformed
        - Etherscan API key was not given
        - Etherscan response is fatal

- Adds support for more L2s
  * Arbitrum (One)
  * Optimism
  * Base

- Adds more L2s to existing accounts
  * Coinbase Wallet
  * Ledger Live
  * MetaMask

- Updates documentation
  * Update default generated `fetch` config
  * Update `fetch` usage help
  * Update README

container/src/hledger-flow/accounts/blockchain-explorers/ethereum-based/ethereum-based-shared.rules

@@ -56,7 +56,7 @@ if %direction ^OUT$
 #     at times, send to the contract address for certain end-user addresses. So,
 #     reports will produce a double-spend unless this is corrected here.
 if %direction ^OUT$
-& %blockchain (^ethereum$|^polygon$)
+& %blockchain (^ethereum$|^polygon$|^arbitrum$|^base$|^optimism$)
 & %type ^normal$
 & %fees [1-9]
   account3 assets:%account_name:%subaccount_name:%blockchain:%symbol
@@ -69,7 +69,7 @@ if %direction ^OUT$
 
 # Remove 0 value txs (or else journal is cluttered). These should appear for FEE spends only
 if %direction ^OUT$
-& %blockchain (^ethereum$|^polygon$)
+& %blockchain (^ethereum$|^polygon$|^arbitrum$|^base$|^optimism$)
 & %amount_ ^[^1-9]*$
   account1
   account2
@@ -99,6 +99,8 @@ if %to_address ^0x401f6c983ea34274ec46f84d70b31c151321188b$
 
 # NOTE: No ERC-20 txs here for WETH... all "normal" or "internal"
 
+# TODO: on all supported chains
+
 # BUY
 if %to_address ^0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2$
 & %blockchain ^ethereum$
@@ -169,6 +171,8 @@ if %to_address ^0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2$
 #                                   Swapping                                   #
 # ---------------------------------------------------------------------------- #
 
+# TODO: on all supported chains
+
 include ./rules.d/swap.d/1inch.rules
 include ./rules.d/swap.d/airswap.rules
 include ./rules.d/swap.d/metamask.rules
@@ -178,6 +182,8 @@ include ./rules.d/swap.d/uniswap.rules
 #                                   Lending                                    #
 # ---------------------------------------------------------------------------- #
 
+# TODO: on all supported chains
+
 include ./rules.d/lending.d/aave.rules
 include ./rules.d/lending.d/compound.rules
 
@@ -185,6 +191,8 @@ include ./rules.d/lending.d/compound.rules
 #                                   Staking                                    #
 # ---------------------------------------------------------------------------- #
 
+# TODO: on all supported chains
+
 include ./rules.d/staking.d/lido.rules
 include ./rules.d/staking.d/rocket-pool.rules