feat: new rule no-useless-coaleascing

[ColemanDunn]

Implements #703

Apologies if opening a PR for a rule like this is a bit hasty, but I wanted to get a proof of concept out to support my issue

AI disclosure: I used codex to help me implement the rules and attempt to match the codebase

quick preview on when this rule is triggered:

type User = {
  name?: string;
  arr?: string[];
};

declare const user: User | undefined;
declare const alwaysString: string;
declare const alwaysArray: string[];
declare const maybeString: string | undefined;
declare const maybeArray: string[] | undefined;

// user.name
const sample1 = user?.name || undefined; // triggers with detectFalsyValues

// always string
const sample2 = alwaysString || ""; // triggers rule
const sample3 = alwaysString || undefined;
const sample4 = alwaysString ?? ""; // triggers rule        -------- triggers no-unnecessary-condition
const sample5 = alwaysString ?? undefined; // triggers rule  -------- triggers no-unnecessary-condition

// maybe string
const sample6 = maybeString || "";
const sample7 = maybeString || undefined; // triggers with detectFalsyValues
const sample8 = maybeString ?? "";
const sample9 = maybeString ?? undefined; // triggers rule

// always array
const sample10 = alwaysArray || []; // triggers rule         -------- triggers no-unnecessary-condition
const sample11 = alwaysArray || undefined; // triggers rule   -------- triggers no-unnecessary-condition
const sample12 = alwaysArray ?? []; // triggers rule         -------- triggers no-unnecessary-condition
const sample13 = alwaysArray ?? undefined; // triggers rule   -------- triggers no-unnecessary-condition

// maybe array
const sample14 = maybeArray || [];
const sample15 = maybeArray || undefined; // triggers rule
const sample16 = maybeArray ?? [];
const sample17 = maybeArray ?? undefined; // triggers rule

// extra ones (to demonstrate no false positives (for this example) etc.)
const sample18 = maybeString || maybeArray;
const sample19 = maybeArray || maybeString;

const sample20 = maybeString || maybeArray || undefined; // triggers with detectFalsyValues
const sample21 = maybeArray || maybeString || undefined; // triggers with detectFalsyValues