VM: Update run-solidity-contract example

[ryanio]

This PR:

• replaces ethereumjs-abi (deprecated) with @ethersproject/abi (closes VM: Update run-solidty example to use Ethers ABI Encoder #1098)
• upgrades solc version
  • fixes some new warnings for contract:
    • upgrades solidity version
    • adds SPDX-License-Identifier
    • removes visibility identifier from constructor (public is default)

---

To test, cd into packages/vm/examples/run-solidity-contract and run npm i && npm run example

The output should look like this:

> run-solidity-contract@ example /Users/rg/dev/ethereumjs-monorepo/packages/vm/examples/run-solidity-contract
> ts-node index.ts

Account: 0xbe862ad9abfe6f22bcb087716c7d89a26051f74c
Set account a balance of 1 ETH
Compiling...
Compiled the contract
Deploying the contract...
Contract address: 0x61de9dc6f6cff1df2809480882cfd3c2364b28f7
Greeting: Hello, World!
Changing greeting...
Greeting: Hola, Mundo!
Everything run correctly!

[codecov]

Codecov Report

Merging #1104 (6f9d570) into master (139d90e) will increase coverage by 0.10%.
The diff coverage is n/a.

Flag	Coverage Δ
block	81.40% <ø> (+0.14%)	⬆️
blockchain	83.44% <ø> (-0.08%)	⬇️
client	86.85% <ø> (+0.20%)	⬆️
common	86.34% <ø> (ø)
devp2p	84.25% <ø> (ø)
ethash	82.08% <ø> (ø)
tx	91.93% <ø> (-0.13%)	⬇️
vm	82.32% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

[alcuadrado]

Great that you updated this! I send people to this example from time to time.

[holgerd77]

Works like a charm, very cool! 😄