feat: read INSTABUG_APP_TOKEN from env in sourcemap uploading

[ahmedAlaaInstabug]

Description of the change

1. support reading INSTABUG_APP_TOKEN variable from env files in automatic sourcemap files uploading

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

JIRA ID: INSD-10736

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests

Code review

• This pull request has a descriptive title and information useful to a reviewer
• Issue from task tracker has a link to this pull request

[InstabugCI]

Coverage Report

Label	Coverage	Status
JavaScript	96.3%	✅
Android	48.3%	✅
iOS	42.3%	✅

Generated by 🚫 dangerJS against 6339f8e

[a7medev]

@ahmedAlaaInstabug Why do we need to configure environment variables in the Gradle project properties on Android? What's the status of this PR?