Move error handling to C code

[qmuntal]

This PR moves most of the error handling to the C side so that we don't have to worry about us retrieving OpenSSL errors from the wrong OpenSSL per-thread error queue (see #231).

The main trick is to autogenerate a new set of C wrappers, for those functions that return an error, with an additional error parameter that will be filled with error context if the function fails. The Go autogenerated functions will convert that error context into a Go error and return it to the caller.

This new error handling approach should have 0 performance impact when there are no errors. In the error situation, expect less allocations thanks to some small improvements I've done to the C ->Go error mapping process:

goos: windows
goarch: amd64
pkg: github.com/golang-fips/openssl/v2
cpu: Intel(R) Core(TM) i7-10850H CPU @ 2.70GHz
         │   old.txt   │               new.txt               │
         │   sec/op    │    sec/op     vs base               │
Error-12   5.035µ ± 1%   4.685µ ± 13%  -6.96% (p=0.019 n=10)

         │   old.txt    │               new.txt                │
         │     B/op     │     B/op      vs base                │
Error-12   2.184Ki ± 0%   1.537Ki ± 0%  -29.61% (p=0.000 n=10)

         │  old.txt   │              new.txt               │
         │ allocs/op  │ allocs/op   vs base                │
Error-12   20.00 ± 0%   10.00 ± 0%  -50.00% (p=0.000 n=10)

Note that this PR almost only changes mkcgo and autogenerated code, as #262 already did the job of refactoring the codebase to construct Go errors in the autogenerated code.

Fixes #231.

[dagood]

Nice! A small handful of minor suggestions.