Simplifies type generation for hooks

[nick-Ag]

This PR addresses an issue that came up when adding object type hook input fields. The type generation couldn't properly define the nested shape of the properties and would incorrectly generate something like this:

export interface HookBundle {
  onMappingSave: {
    [k: string]: unknown
  }
}

In general the HookBundle previously would have a shape such as this:

export interface HookBundle {
  onMappingSave: {
    inputs?: { ... }
    outputs?: { ... }
  }
}

And I've updated it to flatter shape which cleanly generates nested object properties like this:

export interface OnMappingSaveInputs {
  name: string
  ...
  columns?: {
    name: string
    ...
  }[]
}

export interface OnMappingSaveOutputs {
...
}

Testing

This change should be non-functional, since it only applies to action hook types.
Tested successfully in stage against LinkedIn Conversions API: Could successfully create a Conversion rule with the actions onMappingSave hook

• Added unit tests for new functionality
• Tested end-to-end using the local server
• [If destination is already live] Tested for backward compatibility of destination. Note: New required fields are a breaking change.
• [Segmenters] Tested in the staging environment
• [Segmenters] [If applicable for this change] Tested for regression with Hadron.

[codecov]

Codecov Report

Attention: Patch coverage is 14.28571% with 6 lines in your changes missing coverage. Please review.

Project coverage is 79.07%. Comparing base (52537f3) to head (a19c327).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/cli/src/commands/generate/types.ts	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2723      +/-   ##
==========================================
+ Coverage   78.46%   79.07%   +0.61%     
==========================================
  Files        1036     1089      +53     
  Lines       18771    21534    +2763     
  Branches     3561     4312     +751     
==========================================
+ Hits        14729    17029    +2300     
- Misses       2844     3298     +454     
- Partials     1198     1207       +9     

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