refactor: replace axios with ky

[0xbe1]

As KY author said in https://twitter.com/sindresorhus/status/1037763588826398720:

Yes. Axios is based on XMLHttpRequests, while Ky is based on Fetch. Axios has manually implemented a lot of things we get for free with Fetch. Fetch-based libs should be more stable and less buggy in general. Ky also has retry functionality.

for us, ky is desired because:

• 3x smaller bundle size
• built-in retry support https://github.com/sindresorhus/ky#retry
• built-in typescript support https://github.com/sindresorhus/ky#json

so that we can get rid of:

• retryLimit in PoolDataClient.ts