tree: Add export + import tests, fix recursive map schema exports

[CraigMacomber]

Description

TypeScript can have issues that can only be observed by consuming d.ts files (See included README.md).

This change adds an extra TypeScript project so tree tests can export types which are consumed from d.ts files to check if they work.

This functionality was then used to fix recursive map schema exports so that when imported with libCheck enabled, they no longer produce compile errors.

Depends on fluid-build fix in https://github.com/microsoft/FluidFramework/pull/21734 to fix fluid-tsc commonjs --build ./src/test/tsconfig.cjs.json failing with no error output.

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