chore: enable jemalloc by default on unix

[shekhirin]

This PR additionally gates jemallocator usage by unix target family and enables jemalloc feature by default. It means the following:

1. On Unix, use jemallocator if not specified otherwise via --no-default-features .
2. On Windows, use default allocator. If --features jemalloc is specified, ignore it because Windows is not fully supported by jemalloc.

Windows builds successfully: https://github.com/paradigmxyz/reth/actions/runs/5543015346/jobs/10118463541?pr=3735

[mattsse]

I think we want this.

pending @rkrasiuk

[codecov]

Codecov Report

Merging #3735 (785a8a7) into main (e3ac77a) will decrease coverage by 9.86%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
bin/reth/src/main.rs	14.28% <ø> (ø)
bin/reth/src/prometheus_exporter.rs	0.00% <ø> (ø)

... and 161 files with indirect coverage changes

Flag	Coverage Δ
integration-tests	15.78% <ø> (-0.01%)	⬇️
unit-tests	43.90% <ø> (-10.28%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
reth binary	17.67% <ø> (-7.07%)	⬇️
blockchain tree	31.90% <ø> (-9.83%)	⬇️
pipeline	66.86% <ø> (-12.38%)	⬇️
storage (db)	52.49% <ø> (-6.68%)	⬇️
trie	58.76% <ø> (-12.83%)	⬇️
txpool	35.60% <ø> (-8.48%)	⬇️
networking	56.84% <ø> (-11.76%)	⬇️
rpc	44.60% <ø> (-6.82%)	⬇️
consensus	42.73% <ø> (-14.07%)	⬇️
revm	21.22% <ø> (-7.47%)	⬇️
payload builder	6.61% <ø> (ø)
primitives	65.30% <ø> (-13.03%)	⬇️

[onbjerg]

would simplify the makefile too by removing the feature filtering/special handling for windows etc around jemalloc