fix(devtool): specify the host machine port used by explorer service

[sunchengzhu]

What this PR does / why we need it?

The 4020 port of the Docker container is mapped to the 4020 port of the host machine.

What is the impact of this PR?

No Breaking Change

PR relation:

• Ref #

CI Settings

CI Usage

Tip: Check the CI you want to run below, and then comment /run-ci.

CI Switch

• E2E Tests
• Web3 Compatible Tests
• OCT 1-5 And 12-15
• OCT 6-10
• OCT 11
• OCT 16-19
• v3 Core Tests

CI Description

CI Name	Description
Chaos CI	Test the liveness and robustness of Axon under terrible network condition
Cargo Clippy	Run cargo clippy --all --all-targets --all-features
Coverage Test	Get the unit test coverage report
E2E Test	Run end-to-end test to check interfaces
Code Format	Run cargo +nightly fmt --all -- --check and cargo sort -gwc
Web3 Compatible Test	Test the Web3 compatibility of Axon
v3 Core Test	Run the compatibility tests provided by Uniswap V3
OCT 1-5 | 6-10 | 11 | 12-15 | 16-19	Run the compatibility tests provided by OpenZeppelin