perf demangle-rust: Add rustc-demangle C demangler

Imported at commit 80e40f57d99f ("add comment about finding latest
version of code") from:

https://github.com/rust-lang/rustc-demangle/blob/main/crates/native-c/src/demangle.c
https://github.com/rust-lang/rustc-demangle/blob/main/crates/native-c/include/demangle.h

There is discussion of this issue motivating the import in:

https://github.com/rust-lang/rust/issues/60705
https://lore.kernel.org/lkml/20250129193037.573431-1-irogers@google.com/

The SPDX lines reflect the dual license Apache-2 or MIT in:

https://github.com/rust-lang/rustc-demangle/blob/main/README.md

Following Migual Ojeda's suggestion comments were added on copyright and
keeping the code in sync with upstream.

The files are renamed as perf supports multiple demanglers and so
demangle as a name would be overloaded.

The work here was done by Ariel Ben-Yehuda <ariel.byd@gmail.com> and I
am merely importing it as discussed in the rust-lang issue.

Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Ariel Ben-Yehuda <ariel.byd@gmail.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: Bill Wendling <morbo@google.com>
Cc: Björn Roy Baron <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Daniel Xu <dxu@dxuuu.xyz>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Trevor Gross <tmgross@umich.edu>
Link: https://lore.kernel.org/r/20250430004128.474388-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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