The motivation here is that we don't want to pollute the SBAPI with
getters/setters for expression evaluation options that only apply to a
single language. The ultimate goal would be to have plugins register
additional options to the `expression` command when the plugin is
loaded. This patch only provides the minimal `SBExpressionOptions`
interface to set an option with an arbitrary name, which the language
plugin knows how to interpret. The underlying options dictionary is an
`StructuredData::Dictionary` so we can map strings to values of any
type. But the SBAPI just exposes setting a boolean value. Future
overloads of `SetLanguageOption` can provide setters for more types.
The boolean setter/getter will be used for the C++-specific option being
introduced in: https://github.com/llvm/llvm-project/pull/177926
2e52de5aa2