[SDPatternMatch] Do not use std::forward and rvalue references (NFC) (#93806)

The m_ZExtOrSelf() family of matchers currently incorrectly calls
std::forward twice on the same value. However, just removing those causes
other complications, because then template arguments get incorrectly
inferred to const references instead of the underlying value types.
Things become a mess.

Instead, just completely remove the use of std::forward and rvalue
references from SDPatternMatch. I don't think they really provide value
in this context, especially as they're not used consistently in the
first place.