Remove Eager read, write, accept

[ry]

The eager code is very complicated for very little benefit. By removing it, tail latency (which is VERY BAD currently) is reduced by half. Absolute req/sec is slightly slower tho - I still think it makes sense to remove.

Here I'm running ./target/release/deno tests/http_bench.ts -A

Without eager (this branch)

~/src/deno> third_party/wrk/mac/wrk -d 10 -c 10 http:https://127.0.0.1:4500/
Running 10s test @ http:https://127.0.0.1:4500/
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     5.90ms   29.21ms 425.93ms   95.69%
    Req/Sec    16.55k     3.08k   22.18k    83.17%
  332652 requests in 10.10s, 16.18MB read
Requests/sec:  32931.55
Transfer/sec:      1.60MB

With eager (master)

~/src/deno> third_party/wrk/mac/wrk -d 10 -c 10 http:https://127.0.0.1:4500/
Running 10s test @ http:https://127.0.0.1:4500/
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    26.06ms  122.80ms   1.35s    95.18%
    Req/Sec    17.46k     3.01k   24.06k    76.00%
  347308 requests in 10.00s, 16.89MB read
Requests/sec:  34722.65
Transfer/sec:      1.69MB

Furthermore this suggests that maybe the tail latency problems experienced in deno_core_http_bench are due to an over-eager event loop (the while loop in deno_core::Isolate::poll())