[llvm] [CommandLine] Make options of copyable class types get reset to their provided initial values (PR #173026)

[Benjamin Stott via llvm-commits]

BStott6 wrote:

@kuhar now that the `STLExtras` PR is merged (with no test explosions this time), would you mind looking at this again?

https://github.com/llvm/llvm-project/pull/173026