[next] Nested option (`optionDefinitions`) issues

[zFernand0]

1. ConfigSchema APIs may not support nested options In ConfigSchema.parseSchema function... https://github.com/zowe/imperative/blob/cae116c8995e358a5e21ef00c3347ecf47689509/packages/config/src/ConfigSchema.ts#L115

2. Programmers may not be able to defined nested secure properties. For example: banana.origin.country = USA could be in plain text, but plugin developers may want to secure banana.origin.token = secret. However, they have to secure the entire object (banana.origin = ****) https://github.com/zowe/imperative/blob/1210bcd5d46045492764fa5f13070a64529556e7/tests/src/packages/profiles/src/constants/ProfileInfoConstants.ts#L84-L100

3. Users may be able to define nested secure properties. https://github.com/zowe/imperative/blob/1210bcd5d46045492764fa5f13070a64529556e7/tests/src/packages/profiles/src/constants/ProfileInfoConstants.ts#L107-L130