Migrate from ethers-v5 to viem

[piotr-roslaniec]

Type of PR:

• Refactor

Required reviews:

• 3

What this does:

• Replaces dependency on ethers-v5 with viem
• Introduces signer-provider separation with WalletClient and PublicClient

Issues fixed/closed:

• Fixes Introduce provider/signer separation into API #268

Why it's needed:

Explain how this PR fits in the greater context of the NuCypher Network.
E.g., if this PR address a nucypher/productdev issue, let reviewers know!

Notes for reviewers:

• This is just an initial draft
• Remove remainder of ethers usage
• Remove typechain usage (based on ethers)
• Use abitype/zod to validate functionAbi instead of relying on ethers

[codecov-commenter]

Codecov Report

Merging #271 (3796355) into alpha (a98cee4) will decrease coverage by 1.69%.
The diff coverage is 54.83%.

@@            Coverage Diff             @@
##            alpha     #271      +/-   ##
==========================================
- Coverage   80.56%   78.88%   -1.69%     
==========================================
  Files          36       37       +1     
  Lines         983     1042      +59     
  Branches      108      127      +19     
==========================================
+ Hits          792      822      +30     
- Misses        183      206      +23     
- Partials        8       14       +6     

Files Changed	Coverage Δ
src/sdk/strategy/pre-strategy.ts	98.55% <ø> (ø)
src/web3.ts	85.71% <ø> (ø)
src/agents/coordinator.ts	28.88% <20.00%> (+1.61%)	⬆️
src/dkg.ts	29.26% <25.00%> (+1.06%)	⬆️
src/agents/subscription-manager.ts	21.73% <30.76%> (+4.34%)	⬆️
src/viem.ts	31.25% <31.25%> (ø)
src/agents/contracts.ts	42.10% <33.33%> (-4.96%)	⬇️
src/policies/policy.ts	80.00% <44.44%> (-4.32%)	⬇️
src/sdk/strategy/cbd-strategy.ts	93.33% <50.00%> (ø)
src/conditions/context/providers.ts	82.00% <91.66%> (+0.91%)	⬆️
... and 5 more

[piotr-roslaniec]

Closing this stale draft in favor of #421