Use DEEPBIND flag when loading external modules using dlopen

[rjd15372]

The current flags used in dlopen to load external modules don't allow modules to define symbols that are already defined by the valkey server binary because the symbol resolution first looks in the server memory and only if it does not find anything, it looks in the module (shared library) memory.

This might become a problem if, for instance, we try to implement a new scripting engine based on a newer version of Lua. The Lua interpreter library shares many symbol names with the Lua interpreter included in the Valkey server binary.

To fix the above problem, this PR adds the flag RTLD_DEEPBIND to the flags used in dlopen on systems that support it, which changes the symbol resolution strategy to look for the symbol in the module memory first, if the code executing is from the module.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 71.11%. Comparing base (3828936) to head (a221102).
Report is 5 commits behind head on unstable.

Files with missing lines	Patch %	Lines
src/module.c	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           unstable    #1703   +/-   ##
=========================================
  Coverage     71.10%   71.11%           
=========================================
  Files           123      123           
  Lines         65523    65532    +9     
=========================================
+ Hits          46590    46600   +10     
+ Misses        18933    18932    -1     

Files with missing lines	Coverage Δ
src/module.c	9.61% <0.00%> (+<0.01%)	⬆️

... and 12 files with indirect coverage changes

[zuiderkwast]

@rjd15372 Daily job failed:

https://github.com/valkey-io/valkey/actions/runs/13253032412/job/36994775025

==89691==You are trying to dlopen a /home/runner/work/valkey/valkey/tests/modules/reply.so shared library with RTLD_DEEPBIND flag which is incompatible with sanitizer runtime (see google/sanitizers#611 for details). If you want to run /home/runner/work/valkey/valkey/tests/modules/reply.so library under sanitizers please remove RTLD_DEEPBIND from dlopen flags.

[enjoy-binbin]

I see we did skip it, is there anything missing in the condition?

    int dlopen_flags = RTLD_NOW | RTLD_LOCAL;
#if (defined(__linux__) || defined(__FreeBSD__)) && !defined(__SANITIZE_ADDRESS__)
    /* RTLD_DEEPBIND, which is required for loading modules that contains the
     * same symbols, does not work with ASAN. Therefore, we exclude
     * RTLD_DEEPBIND when doing test builds with ASAN.
     * See https://github.com/google/sanitizers/issues/611 for more details.
     *
     * This flag is also currently only available in Linux and FreeBSD. */
    dlopen_flags |= RTLD_DEEPBIND;
#endif

[zuiderkwast]

@enjoy-binbin see this: #1707