Upgrade ethers v5 -> v6

[danielbate]

Ethers v6 came out earlier in the year so we should upgrade to future proof and benefit from the additional optimisations that come from the version upgrade, such as ES module support that will aid our efforts to support browser testing (pre-requisite for Vitest implementation #813). v6 has also cleaned up a lot of the code and brought stricter function signatures so seems to have been developed with defensive programming in mind.

[danielbate]

Upgrades:

• sha
• pbkdf2
• network
• basex
• bytes (BytesLike)
• hexSlide
• hexlify

Remove:

• abi
• bignumber
• properties
• strings
• logger - our own errors package should take precedence (take care of via refactor: using FuelError instead of @ethersproject/logger #1278)

Augment:

• arrayify - now getBytesCopy (getBtyesCopy is used over getBytes to avoid issues where a Buffer could be passed in and is then not returned as a UInt8Array)
• concat - the function signature has been made stricter here and now only returns a string, we should look to implement our own bytes concatenation function also