Include SDK generation as part of firebase init dataconnect

[rosalyntan]

Description

Include firebase init dataconnect:sdk functionality as part of firebase init dataconnect.

Also updated the app directory prompt: "Where is your app directory? Leave blank to set up a generated SDK in your current directory."

Scenarios Tested

• firebase init dataconnect in a folder with build.gradle
• firebase init dataconnect in a folder without platform indicators, (y) when prompted for gen SDKs
• firebase init dataconnect in a folder without platform indicators, (n) when prompted for gen SDKs

Sample Commands

firebase init dataconnect in a folder with build.gradle:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 40.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 56.75%. Comparing base (18e3189) to head (27300d0).
Report is 26 commits behind head on master.

Files with missing lines	Patch %	Lines
src/init/features/dataconnect/index.ts	33.33%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7693      +/-   ##
==========================================
- Coverage   56.91%   56.75%   -0.17%     
==========================================
  Files         396      396              
  Lines       27599    27726     +127     
  Branches     5692     5737      +45     
==========================================
+ Hits        15708    15735      +27     
- Misses      11723    11822      +99     
- Partials      168      169       +1     

Flag	Coverage Δ
	56.75% <40.00%> (?)

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