[PORT][Expression]Enable list concatenation for function "concat"

[Danieladu]

Fixes #2373

concat:

1. If all items are lists, concatenate them with list mode.
   concat([1, 2], [3, 4]) -> [1, 2, 3, 4]

2. If there exists any item that is not a list, use string concatenation mode:
   concat('a', 'b', 1, 2) -> 'ab12'
concat('a', [1, 2]) -> aSystem.Collections.Generic.List 1[System.Object] // unreadable, best to avoid

3. If null exists, skip it
   concat([1, 2], null) -> [1, 2]
concat('a', 1, null) -> 'a1'

[coveralls]

Pull Request Test Coverage Report for Build 139491

• 19 of 20 (95.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 80.917%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/adaptive-expressions/src/expressionFunctions.ts	19	20	95.0%

Totals
Change from base Build 139207:	0.02%
Covered Lines:	12882
Relevant Lines:	15204

---

💛 - Coveralls

[chrimc62]

[chrimc62]

(input === null || input === undefined [](start = 11, length = 38)

!input would be clearer and more idiomatic. It is also fine for the empty string case.

[Danieladu]

but it is not fine for the boolean type false