Reland [lldb] Unify type name matching in FormattersContainer

This was originally reverted because the Linux bots were red after this landed,
but it seems that was actually caused by a different commit. I double checked
that this works on Linux, so let's reland this on Linux.

Summary:

FormattersContainer stores LLDB's formatters. It's implemented as a templated
map-like data structures that supports any kind of value type and only allows
ConstString and RegularExpression as the key types. The keys are used for
matching type names (e.g., the ConstString key `std::vector` matches the type
with the same name while RegularExpression keys match any type where the
RegularExpression instance matches).

The fact that a single FormattersContainer can only match either by string
comparison or regex matching (depending on the KeyType) causes us to always have
two FormatterContainer instances in all the formatting code. This also leads to
us having every type name matching logic in LLDB twice. For example,
TypeCate...