test: investigate slow request handler imports

[galargh]

• Because this PR includes a bug fix, relevant tests have been included.
• Because this PR includes a new feature, the change was previously discussed on an Issue or with someone from the team.
• I didn't do anything of this.

---

Related to #6211

In 92ceb85, I set up a test which measures the import times of request handlers. It is not ideal but good enough to give us some data to work with.

By analyzing the results, it is clear that the Local Accounts Handler is the main culprit of the slow imports (the HD Wallet Accounts Handler imports the Local Accounts Handler which makes it slow by association).

As an exercise, I was able to shave off 1/3 of the loading time from the Local Accounts Handler by making the micro-eth-signer imports dynamic in 4d429a1. It shows that it is possible (and we could definitely do that for some other import paths there), but I'm not entirely sure we should go down that route.

I think we might be better off with the original solution to this, which is to use dynamic imports for handlers in the handlers array.

Here are the raw results of the handler import time analysis:

hardhat/v-next/hardhat/test/internal/builtin-plugins/network-manager/request-handlers/handlers-array.ts

Lines 13 to 27 in 92ceb85

	/**
	* Example debug output:
	* 2025-03-18T10:54:37.575Z hardhat:test:network-manager:request-handlers:request-array importing hd-wallet-handler.ts took 37ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing local-accounts.ts took 36ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing fixed-sender-handler.ts took 11ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing chain-id-handler.ts took 11ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing chain-id.ts took 11ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing automatic-gas-handler.ts took 11ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing automatic-gas-price-handler.ts took 11ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing fixed-gas-handler.ts took 11ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing automatic-sender-handler.ts took 10ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing sender.ts took 10ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing fixed-gas-price-handler.ts took 10ms
	* 2025-03-18T10:54:37.576Z hardhat:test:network-manager:request-handlers:request-array importing multiplied-gas-estimation.ts took 10ms
	*/

I'm leaving this PR in draft as it was useful to me during the investigation. I don't necesarilly want to merge it as I think it would be a pretty flaky addition. We can discuss the next steps either here or in the original issue.

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Name	Status	Preview	Comments	Updated (UTC)
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