[lldb] Thread mangling flavor together with node pointer

[augusto2112]

LLDB performs many analysis as transformations by converting a mangled
name into a demangle tree and later on back to a mangled name.
Unfortunately there's no cheap way for a demangle tree to carry its
mangled name's mangling flavor. This patch threads the mangling flavor
along with the demangle tree so when converting a demangle tree back to
a mangled name we reconstruct it with the same mangling flavor as the
original type.

[augusto2112]

@swift-ci test

[kubamracek]

@swift-ci test Windows platform

[kubamracek]

@swift-ci test Windows platform

[adrian-prantl]

I have one rather fundamental question. Instead of threading this through as a parameter, should embedded Swift be a separate Language with a separate TypeSystemSwift instance (that uses the same implementation, but hardcodes the flavor)?
If we never intend to mix&match between the two, why try to have one typesystem instance deal with both?

[kubamracek]

@swift-ci test

[kubamracek]

@swift-ci test

[augusto2112]

@swift-ci test

[kubamracek]

@swift-ci test macOS platform