refactor: replace retry with internal async backoff retry loop

[joehan]

Description

Removed the external third-party retry and @types/retry dependencies and replaced them with a native async retry loop with exponential backoff inside src/apiv2.ts.

Scenarios Tested

• Run all src/apiv2.spec.ts unit tests successfully.

Sample Commands

• npx mocha src/apiv2.spec.ts

[gemini-code-assist]

Code Review

This pull request removes the external retry dependency and replaces its usage in src/apiv2.ts with a custom retry loop using a while (true) block and a sleep utility. The review feedback suggests avoiding the use of any in catch blocks to comply with the repository's TypeScript guidelines, and improving error wrapping in FirebaseError to preserve the original stack trace and error details.

[gemini-code-assist]

Avoid using any as an escape hatch per the TypeScript guidelines in the repository style guide. We should type the caught variable as unknown and use a safe conversion to Error to ensure type safety.

Suggested change

	} catch (thrown: any) {
	const err = thrown instanceof Error ? thrown : new Error(thrown);
	} catch (thrown: unknown) {
	const err = thrown instanceof Error ? thrown : new Error(String(thrown));

References

1. Never use any or unknown as an escape hatch. Define proper interfaces/types or use type guards. ^(link)

[gemini-code-assist]

When wrapping a generic caught error in a FirebaseError, using new FirebaseError(${err}) converts the error to a string (which includes the error name, e.g., "Error: message") and discards the original stack trace.

Instead, we should check if the caught error is an instance of Error and pass it as the original property to preserve the stack trace and original error details.

      } catch (err: unknown) {
        if (err instanceof FirebaseError) {
          throw err;
        }
        if (err instanceof Error) {
          throw new FirebaseError(err.message, { original: err });
        }
        throw new FirebaseError(String(err));
      }