Enable client eviction by default, set maxmemory-clients too 100% by default

[enjoy-binbin]

The client eviction introduced in 2753429,
at that time, the main idea of our introduction was to protect key data
from being evicted, which is the server's perspective.

In fact, the accumulated client output buffer can also violate the maxmemory
contract and causing the machine to OOM.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.04%. Comparing base (bcd2f95) to head (ac08340).

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1840      +/-   ##
============================================
+ Coverage     70.97%   71.04%   +0.06%     
============================================
  Files           123      123              
  Lines         65665    65665              
============================================
+ Hits          46608    46649      +41     
+ Misses        19057    19016      -41     

Files with missing lines	Coverage Δ
src/config.c	78.77% <ø> (+0.38%)	⬆️

... and 11 files with indirect coverage changes

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[hwware]

I am not sure if 100% as default value is reasonable

[hpatro]

I think we shouldn't enable it by default. It cause throughput degradation (extra cpu cycle during command processing) due to constant tracking/metric update of client's input/output buffer size during read/write flow.

redis/redis#11348