Decision on whether parsing should be case-sensitive

[vlada-shubina]

The current parser is case sensitive: --Nullable and --nullable are different options.
We need to decide whether to keep it so with new parser.

If we decide to keep parser case-sensitive, we should probably adopt naming symbols with small character in template.json, to avoid putting entry in dotnetcli.host.json just for case change, and make respective changes in the templates (for example now we have Framework, but langVersion). Alternatively, we can change the case of first letter programmatically.

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Originally posted by @vlada-shubina in #3173 (comment)

[RussKie]

I find case sensitivity on Windows rather surprising. E.g. this caught me off-guard:

[sayedihashimi]

I found that being case sensitive was very unexpected.

[vlada-shubina]

No change to this behavior is planned in scope of #2191, keeping the issue opened for discussions.

[YuliiaKovalova]

Close with Low Priority + no major feedback has been received.