Update SDK and Pond to latest dependencies

[ostollmann]

This updates @actyx/sdk and @actyx/pond to the latest dependencies, including:

• rxjs: 5 -> 7
• fp-ts: 1 -> 2
• io-ts: 1 -> 2

This also changes Node from v12.19.0 to v16.13.1.
This also turns rxjs into a bundled dependency of the pond (like the SDK does).
All tests pass. Validation fails because the Pond still uses the old published SDK (vs. the updated one here).

PRE-MERGE MUST DOS:

• remove the @next @actyx/sdk dependency in Pond (just added for integration tests)
• add a changelog

[rkuhn]

wow, this is a lot — I skimmed most of it and checked a few places; now I’ll try and merge master into this get my hands dirty

[ostollmann]

Commit msg:

perf(sdk): upgrade to latest fp-ts and RxJS
perf(pond): upgrade to latest fp-ts and RxJS
feat(sdk): add subscribeAql function to perform AQL-based subscriptions