Clean up leak-detective whitelist for newer Botan versions but add
`botan_private_key_load` as `botan_privkey_load*` won't show up anymore
without bfd-backtraces due to inlining if we don't call it directly.
Ref: https://github.com/randombit/botan/discussions/4868
We keep MD5 enabled for now as we need it for TLS 1.0/1.1. Once we
remove that we can reconsider (although, it's also needed for EAP-MD5
and since MD4 is disabled as well, which means EAP-MSCHAPv2 won't
be available, we'd be left with only EAP-GTC for simple username/password
authentication, which nobody else supports).
The all-zero Ed25519 public key is rejected by botan_pubkey_check_key()
when the key is loaded.
Note that Botan 3 requires GCC 11 or CLANG 14, i.e. can't easily be built
on Debian bullseye or Ubuntu 20.04.
The thread-local storage function gets flagged via various botan FFI
functions when using Botan 3, whitelist that instead of all of them.
If we check out and build a certain revision of a dependency in a branch and
switch to another that requires a different revision and then switch back,
the previous approach installed the wrong revision as it would incorrectly
assume the required revision was already built and ready to install.
ldconfig is required, otherwise the library won't be found by
strongSwan in the same session.
Should later be changed to 2.8.0 or a newer stable release.