Remove last open read cache

[JosiahWI]

It was discussed in #13061 that the one disk read rarely saved with the last open read cache is probably fine on today's SSDs. Removing the optimization simplifies the cache.

Fixes #13095

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[masaori335]

Our benchmark says below.

Scenario	no last-open-read	10.2.0 (vanilla)	Δ
max-tps-10url (plain text)	441,754 req/s	564,269 req/s	−122,515 req/s (−21.7%)
max-tps-10url-tls	505,910 req/s	505,717 req/s	+193 req/s (+0.0%)
max-tps-10url-h2	463,392 req/s	465,356 req/s	−1,964 req/s (−0.4%)
max-tps-100url (plain text)	514,221 req/s	578,793 req/s	−64,572 req/s (−11.2%)
max-tps-100url-tls	517,851 req/s	524,341 req/s	−6,490 req/s (−1.2%)
max-tps-100url-h2	481,452 req/s	487,708 req/s	−6,256 req/s (−1.3%)

Hardware & Config Info

• CPU: Intel(R) Xeon(R) Gold 5218 64 core
• 40 Stripes = 8 (NVME SSD Drive) x 5 (Volumes)
• Thread configs in records.yaml

  exec_thread:
    affinity: 4
    limit: 63
    listen: 1

The mini-cache (last-open-read) is working even if target URL is 100. Now, I'm wondering we should fix the small RAM cache promotion bug and keep this mini cache.