Replace linkedlist for takenbuffer with fixed array

[var77]

• Replace takenbuffers linked list with fixed size (m*2) array and release unused buffers when pinning new ones after the array is filled.
• Remove unused htab and fa_cache instances in retriever context
• Only lock buffers when getting nodes if LANTERNDB_COPYNODES is enabled

TODO

• fix LANTERNDB_COPYNODES path, currently tests are failing with incorrect scan results

[github-actions]

Benchmarks

metric	old	new	pct change
recall (after create)	0.951	0.943	-0.84%
recall (after insert)	0.000	0.000	-
select tps	22287.227	25784.272	+15.69%
select bulk(100) tps	34.705	39.108	+12.69%
select latency (ms)	0.792 ± 1.649𝜎	0.818 ± 1.760𝜎	+3.28%
select bulk(100) latency (ms)	909.948 ± 118.369𝜎	789.290 ± 113.334𝜎	-13.26%
create latency (ms)	401926.841	401222.500	-0.18%
insert tps	438.335	541.854	+23.62%
insert bulk(100) tps	4.551	5.537	+21.67%
insert latency (ms)	72.304 ± 15.802𝜎	58.199 ± 13.234𝜎	-19.51%
insert bulk(100) latency (ms)	6844.376 ± 193.644𝜎	5654.672 ± 112.456𝜎	-17.38%
disk usage (bytes)	8192008192.000	8192008192.000	-

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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