Change how unwind information is stored on Windows (#4314)

* Change how unwind information is stored on Windows

Unwind information on Windows is stored in two separate locations. The
first location is the unwind information itself which corresponds to
`UNWIND_INFO`. The second location is a list of `RUNTIME_INFO`
structures which point to function bodes and `UNWIND_INFO` structures.

Currently in Wasmtime the `UNWIND_INFO` structures are stored just after
functions themselves with a somewhat cryptic comment indicating that
Windows prefers this (I'm unsure as to the provenance of this comment).
The `RUNTIME_INFO` data is then stored in a separate section which has
the custom name of `_wasmtime_winx64_unwind`.

After my recent foray into trying to debug windows-2022 bad unwind
information again I realized though that Windows actually has official
sections for these two unwind information items. The `.xdata` section is
used to store the `UNWIND_INFO` structures and the `.pdata` section
stores the `RUNTIME_INFO` list. To try to be somewhat idiomatic and
perhaps one day even hook into standard Windows debugging tools I went
ahead and refactored how our unwind information is stored to match this.

Perhaps the main benefit of this is that it reduces the size of the
read/execute section of the binary. Previously the unwind information
was executable since it was stored in the `.text` section, but
unnecessarily so. Now it's in a read-only section which is in theory a
small amount of hardening.

Otherwise though I don't think this will really help all that much to
hook up in to standard debugging tools like `objdump` because it's all
still stored in an ELF file rather than a COFF file.

* Review comments

crates/jit/src/unwind/winx64.rs

@@ -33,7 +33,7 @@ impl UnwindRegistration {
     }
 
     pub fn section_name() -> &'static str {
-        "_wasmtime_winx64_unwind"
+        ".pdata"
     }
 }