BREAKING: Move all internal types from snaps-types to snaps-utils

[Mrtenz]

This is a prerequisite for #1014.

I've moved all types from snaps-types to snaps-utils, to avoid circular dependencies. snaps-types has also been refactored to a "regular" package, rather than a type-only package. Even though it still only contains types, this was required for it to be able to import from other monorepo packages.

Breaking changes

• OnRpcRequestHandler, OnTransactionResponse, OnTransactionHandler, and OnCronjobHandler were using unknown[] | Record<string, unknown>. Since values need to be JSON-compatible, I've changed this to Json[] | Record<string, Json>.
• SnapRpcHandler was removed. This seemed like a legacy type, and was the same as OnRpcRequestHandler.
• global.d.ts in snaps-types was removed, as it is no longer necessary. snaps-types creates the globals when the package itself is imported, meaning that the following works now:

  import { OnRpcRequestHandler } from '@metamask/snaps-types';
  
  // Since `@metamask/snaps-types` is imported, the `snap` global is declared.
  snap.request();

• SnapFunctionExports and SnapExports are no longer exported from snaps-types.

Closes #1054.
Closes #815.

[codecov-commenter]

Codecov Report

Merging #1060 (636d095) into main (f39d07e) will decrease coverage by 1.16%.
The diff coverage is 5.30%.

@@            Coverage Diff             @@
##             main    #1060      +/-   ##
==========================================
- Coverage   93.52%   92.36%   -1.17%     
==========================================
  Files          95       96       +1     
  Lines        9922    10044     +122     
  Branches      941      942       +1     
==========================================
- Hits         9280     9277       -3     
- Misses        642      767     +125     

Impacted Files	Coverage Δ
packages/snaps-utils/src/handlers.ts	0.00% <0.00%> (ø)
...cution-environments/src/common/BaseSnapExecutor.ts	92.12% <100.00%> (+0.01%)	⬆️
...cution-environments/src/common/endowments/index.ts	100.00% <100.00%> (ø)
...snaps-execution-environments/src/common/keyring.ts	100.00% <100.00%> (ø)
...ps-execution-environments/src/common/validation.ts	100.00% <100.00%> (ø)
packages/snaps-utils/src/types.ts	100.00% <100.00%> (ø)

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[FrederikBolding]

Needs a rebase but otherwise lgtm