7203 - Alchemy rpc provider

[MRLab12]

Description

I have opened this Draft PR to make sure I did the correct changes and get some feedback since this is my first contribution here.

This PR adds an Alchemy provider in web3-rpc-providers. I matched the design of the Quicknode provider.

For testing, I wasn't sure if a test for this provider should actually try to make a request. Should we consider mocking? I want to learn more about how testing is done in web3.js.

Fixes #7203

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] I have selected the correct base branch.
• [x] I have performed a self-review of my own code.
• [ ] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [ ] Any dependent changes have been merged and published in downstream modules.
• [x] I ran npm run lint with success and extended the tests and types if necessary.
• [ ] I ran npm run test:unit with success.
• [ ] I ran npm run test:coverage and my test cases cover all the lines and branches of the added code.
• [ ] I ran npm run build and tested dist/web3.min.js in a browser.
• [ ] I have tested my code on the live network.
• [ ] I have checked the Deploy Preview and it looks correct.
• [ ] I have updated the CHANGELOG.md file in the root folder.
• [x] I have linked Issue(s) with this PR in "Linked Issues" menu.