[TM-223] Add 'case' statement

Description

This PR attempts to add a case statement to Indigo. Initially attempt was made to add a case expression, but the types didn't work out. So this PR contains a wip attempt to implement it as a statement.

Basically this piggybacks on the case instruction for Lorentz, and just adapts it to use in Indigo. So this PR adds a type IndigoCaseClauseL which is just a wrapper for the CaseClauseL type that the Lorentz case instruction uses. And then, when creating the IndigoM value, we use the Lorentz case_ function to generate embedded code.

Related issue(s)

https://issues.serokell.io/issue/TM-223

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