Move the deprecated stream tests into their own compilation unit.  This
will allow us to disable any preprocessor directives that apply to
deprecation just for these tests (eg, disabling `GIT_DEPRECATED_HARD`).

Avoid the deprecated `git_stream_cb` typedef since we want to compile
the library without deprecated functions or types.  Instead, we can
unroll the alias to its actual type.

Add `@deprecated` to the functions that are, so that they'll appear that
way in docurium.

`git_stream_register_tls` is now deprecated; mark it in an if guard with
the deprecation.

This should not be included in `deprecated.h` since it is an uncommonly
used `sys` header file.

Don't use deprecated constants

Follow up for PR #4917.

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Fix VS warning C4098: 'giterr_set_str' : void function returning a value

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Move `giterr` to `git_error`

Update GITERR and giterr usages in the static code analysis tools to use
the new names.

Move to the `git_error` name in the internal API for error-related
functions.

Replace the `GITERR` values with a `const int` to deprecate error
values.

Move to the `git_error` name in error-related functions, deprecating the
`giterr` functions.  This means, for example, that `giterr_last` is now
`git_error_last`.  The old names are retained for compatibility.

This only updates the public API; internal API and function usage
remains unchanged.

odb: Fix odb foreach to also close on positive error code

In include/git2/odb.h it states that callback can also return
positive value which should break looping.

Implementations of git_odb_foreach() and pack_backend__foreach()
did not respect that.

repository: free memory in symlink detection function

ci: update poxyproxy, run in quiet mode

Update the proxy so that we can enable a quiet mode.

Add/multiply with overflow tweaks

Improve deprecation of old enums

Correct the documentation on the fallback add/multiply with overflow
functions.

Windows provides <intsafe.h> which provides "performant" add and
multiply with overflow operations.  Use them when possible.

Use the smallest unsigned type that is equivalent to `size_t` to
simplify the conditionals.  Error if we're on a system that we believe
offers builtins but we cannot determine which one to use.

The C standard does not specify whether an enum is a signed or unsigned
type.  Obviously, any enum that includes negative values _must_ be
signed, but if all values are positive then the compiler is free to
choose signed or unsigned.

Thus, by changing the type signatures to `git_object_t` and declaring
the old `GIT_OBJ_` values as a signed or unsigned int, we risk a
mismatch between what the compiler has chosen for a `git_object_t`'s
type and our type declaration.

Thus, we declare the deprecated values as the enum instead of guessing.

Recent GCC enables `-Wunused-const-variables`, which makes output quite
noisy.  Disable unused warnings for our deprecated variables.

Move `git_ref_t` to `git_reference_t`

More `git_obj` to `git_object` updates

ci: only run invasive tests in nightly