refactor(EvmBuilder): Remove unnecessary BuilderStage trait

[rakita]

The trait is not needed, so we can remove it.

[github-actions]

Valgrind Results:

==4010== Cachegrind, a cache and branch-prediction profiler
==4010== Copyright (C) 2002-2017, and GNU GPL'd, by Nicholas Nethercote et al.
==4010== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==4010== Command: target/release/snailtracer
==4010== 
--4010-- warning: L3 cache found, using its data for the LL simulation.
Snailtracer Host+Interpreter benchmark (2.1s) ...            not enough samples
==4010== 
==4010== I   refs:      455,348,071
==4010== I1  misses:          4,567
==4010== LLi misses:          2,889
==4010== I1  miss rate:        0.00%
==4010== LLi miss rate:        0.00%
==4010== 
==4010== D   refs:      237,388,463  (160,564,998 rd   + 76,823,465 wr)
==4010== D1  misses:        349,240  (    208,935 rd   +    140,305 wr)
==4010== LLd misses:        137,562  (      4,049 rd   +    133,513 wr)
==4010== D1  miss rate:         0.1% (        0.1%     +        0.2%  )
==4010== LLd miss rate:         0.1% (        0.0%     +        0.2%  )
==4010== 
==4010== LL refs:           353,807  (    213,502 rd   +    140,305 wr)
==4010== LL misses:         140,451  (      6,938 rd   +    133,513 wr)
==4010== LL miss rate:          0.0% (        0.0%     +        0.2%  )