[Coverity] Medium issues in GPU Plugin (#30447)
### Details:
- Fixing 1565213, 1565100, 1565332
- Other issues are already fixed
### Changes:
- Initialized the default `m_compressed` value to false
- Null pointer dereferences: ensure `compressed_cache_variable` is not
NULL
- Ensure result is float
### Tickets:
- *CVS-157248*
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Co-authored-by: Roman Lyamin <Roman.Lyamin@intel.com>
Co-authored-by: Pavel Durandin <pavel.durandin@intel.com>
