Time Series Insights Instances client library implementation

[barustum]

Here are some things to keep in mind before/while you are reviewing this PR:

• Swagger and examples: https://github.com/Azure/azure-rest-api-specs/tree/master/specification/timeseriesinsights/data-plane/Microsoft.TimeSeriesInsights/stable/2020-07-31
• I would start with reviewing TimeSeriesId classes. Client library implementation references TimeSeriesId classes often, so it'll be useful to know these before other things. If there are unclear pieces of code that you comment on, it means I lack documentation in explaining what a piece of code does. So please do let me know if there is anything unclear
• If you need a refresher on what Time Series Id is, or any TSI related topic, please reach out to me or Binal
• The design of TimeSeriesId classes are yet to be finalized as we are discussing with Krzysztof alternative designs
• This PR does not include the implementation of the Search API. I will do Search in a separate change
• Client libraries are like jokes. If you have to explain them, it isn't that good :). So let me know if things are unclear and we can work on making them clearer.

[bikamani]

Added few comments, looks good otherwise

[bikamani]

Something I just noticed now, did you intend to create a separate API for "replace" or combined for "create and replace"?

Looking at code at line: 772

[bikamani]

Actually looking at swagger, I realize there is put (createOrreplace and update (just replace) - which is super confusing.