15ac916642f20918f66e32729bb6b0b674e3bc24 doc: Doxygen-friendly descriptor.h comments (Jon Layton)
Pull request description:
Closes #16942.
- Make `Descriptor` overview subtext of `Interface for parsed descriptor objects.`
- Conform to `@param[in, out] argname: Info` in parameter comments. Present in code: https://github.com/bitcoin/bitcoin/blob/feb162d500273040c8a2e5cdd3393edf34dff45b/src/net_processing.cpp#L1001
- Remove redundant argument type, `in` vs `out` mentions
- Removed unnecessary backticks around `IsSolvable()`, since Doxygen builds a link to the known function's docs
- Add backticks to refer to `argname`s
`descriptor.cpp` has more documentation, but Doxygen's output doesn't include anything inside unnamed namespaces for some reason. Tried to access them via searchbar.
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Backport of Core PR16947