[lldb] fix dead lock in TypeCategoryMap.cpp (#87540)

FormatManager::GetCategoryForLanguage and
FormatManager::GetCategory(can_create = true) can be called concurrently
and they both take the TypeCategory::m_map_mutex and the
FormatManager::m_language_categories_mutex but in reverse order.

On one thread, GetCategoryForLanguage takes m_language_categories_mutex
and then ends calling TypeCategoryMap::Get which takes m_map_mutex

On another thread GetCategory calls TypeCategoryMap::Add which takes
m_map_mutex and then calls FormatManager::Changed() which takes
m_language_categories_mutex

If both threads are running concurrently, we have a dead lock.

The patch releases the m_map_mutex before calling Changed which avoids
the dead lock.

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Co-authored-by: Vincent Belliard <v-bulle@github.com>