Fixes errors when generating TypeScript components

[liamrathke]

What this PR does / why we need it:

Currently, TypeScript component generation leads to TS components that do not compile, meaning that it is not possible to write plugins for the latest version of Octant in TypeScript. This PR fixes two bugs preventing TS component generation:

• Recursive/nested component types yielding incorrect code (FormFieldConfig is imported and redeclared, causing errors)
• Under specific conditions, variable names from Go code are interjected into the generated TypeScript files, causing errors

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Testing Steps:

• Follow the steps in https://github.com/vmware-tanzu/plugin-library-for-octant/tree/main/yeoman-generator to set up a TypeScript plugin on your local environment
• Inside your new plugin, replace node_modules/@project-octant/plugin/helpers.ts with the latest version (available here)
• Checkout this branch on your local environment
• Run go run ./cmd/ts-component-gen/main.go -dest <directory> to generate TypeScript components, where <directory> is the path to node_modules/@project-octant/plugin/components inside your local TypeScript plugin
• Verify that the plugin compiles and displays correctly

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Which issue(s) this PR fixes

• https://kubernetes.slack.com/archives/CM37M9FCG/p1624388160066200
• Adds form component to generated components #2583 (redo of previous PR after consulting with @GuessWhoSamFoo)