Remove some unused build options

[AlysonStahl-NOAA]

Part of #497

Removes:
USE_TIGGE
USE_MYSQL
USE_WMO_VALIDATION
DISABLE_TIMEZONE

[Copilot]

Pull request overview

This PR removes four unused or always-available build options from wgrib2 as part of build system cleanup efforts (issue #497): USE_TIGGE, USE_MYSQL, USE_WMO_VALIDATION, and DISABLE_TIMEZONE.

Changes:

• TIGGE functionality is now always available instead of being optional
• MySQL support for the extra build is now auto-detected rather than manually configured
• WMO_VALIDATION and DISABLE_TIMEZONE build options are removed from CMake configuration

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
wgrib2/wgrib2_meta.h.in	Removes cmakedefine directives for USE_TIGGE, USE_MYSQL, USE_WMO_VALIDATION, and DISABLE_TIMEZONE
wgrib2/config.h.in	Removes cmakedefine directives for the removed build options
wgrib2/init.c	Removes USE_TIGGE conditional compilation guards around tigge variable declarations
wgrib2/gribtab.c	Removes USE_TIGGE guards around tigge_gribtable definition, making it always available
wgrib2/cname.c	Removes USE_TIGGE guards from getName_all function to make tigge table always accessible
wgrib2/Tigge.c	Removes USE_TIGGE guards and the conditional error branch, making tigge functionality unconditional
wgrib2/Config.c	Removes output messages about USE_MYSQL and USE_TIGGE from configuration display
CMakeLists.txt	Removes option declarations for USE_TIGGE, USE_MYSQL, USE_WMO_VALIDATION, and DISABLE_TIMEZONE
docs/user_guide.md	Removes documentation for the removed build options
spack/package.py	Adds version constraints (@:3.8) to deprecated variants so they only apply to older versions
extra/CMakeLists.txt	Implements automatic MySQL detection with find_package instead of manual configuration

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