fix(cpp): complete and adopt bounded lru cache

[Rayan-and-beyond]

closes #943

this finishes the existing c++ lru cache contract and puts it on the reader device-node path.

• fixes the broken lookup apis and adds explicit non-copying pointer/reference access
• documents caller-side synchronization, reference lifetime, elasticity, and unbounded mode
• removes the stale metadataquerier cache wiring that used std::mutex as the map type
• replaces the reader's unbounded shared-arena device cache with a 64-entry lru where each entry owns its arena, so eviction can actually reclaim metadata pages
• adds focused lru behavior coverage plus a reader regression that fills past capacity, reloads an evicted device, and checks reader metadata memory stays flat

validation:

• 6/6 focused lrucache gtests pass
• device-node bounded/reload regression passes
• full TsFile_Test target builds successfully with -j1 on the constrained vm
• changed production objects compile and libtsfile links with optional codecs/antlr disabled
• git diff --check clean

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