Allow for setting rn-context load time in DetoxTest

[d4vidi]

• This is a small change
• This change has been discussed in issue #<?> and the solution has been agreed upon with maintainers.

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Description:
Resolves #2197. Migrates Detox' idle-policy config to a more generic config structure (that handles idle-policy as well), such that it can also hold a custom timeout for waiting for RN's loading to complete. That enables, for example, the customization of the timeout based on whether the app running in debug mode rather than release - where this can take longer for large apps. See here.

[d4vidi]

@swabbass

[swabbass]

• This is a small change
• This change has been discussed in issue #<?> and the solution has been agreed upon with maintainers.

Description:
Resolves #2197. Migrates Detox' idle-policy config to a more generic config structure (that handles idle-policy as well), such that it can also hold a custom timeout for waiting for RN's loading to complete. That enables, for example, the customization of the timeout based on whether the app running in debug mode rather than release - where this can take longer for large apps. See here.

THX A LOT Wating for this to release to use it.
not a reviewer but wrote my thoughts on kotlin code might be useful :],

[coveralls]

Pull Request Test Coverage Report for Build 2506

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 85.661%

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Totals
Change from base Build 1315:	0.04%
Covered Lines:	3636
Relevant Lines:	4080

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💛 - Coveralls