[typescript][typescript-node] Serialize/deserialize maps and nullable types correctly

[simon-abbott]

There was an edge case in the ObjectSerializer in both the typescript and typescript-node generators where schema objects (object types defined in schema.components) were not properly deserialized if they were contained within a map (an object with additionalProperties) or a nullable array (an array where every entry is either a schema object or null). In these cases the ObjectSerializer would short-circuit and not actually deserialize the object. This results in the snake_cased keys in the API not being converted to the camelCase variants actually documented in the generated typescript types.

I have included tests that cover this (and other) potential encoding and decoding edge cases. I'm sure I didn't cover every possible example, but I did confirm that as-written it will prevent a regression of this issue.

Note: I also removed the TS config setting suppressImplicitAnyIndexErrors from the templates. This was done because suppressImplicitAnyIndexErrors is deprecated, and trying to build with it causes the typescript compiler to error, which was blocking the typescript-node tests from running.

PR checklist

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Mentioning the TS committee members as per the checklist:

@TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny @topce @akehir @petejohansonxo @amakhrov @davidgamero @mkusaka