Moves accounts-db test-only code into a dev-context-only-utils feature

[brooksprumo]

Problem

To prepare for splitting the runtime crate, we'll need access to some private/test-only functions from accounts-db. To simplify that move, we can consolidate the test-only code within accounts-db into dev-context-only-utils feature blocks.

Summary of Changes

Moves all the test-only code into dev-context-only-utils feature blocks, and update the callers.

Refer to #32169 for more information about dev-context-only-utils.

Note, this diff is large. No actual implementations changed. There is a lot of moving code. There is some changing private to public (but only public within a test-only feature).

[codecov]

Codecov Report

Merging #32718 (3fec797) into master (533f42d) will increase coverage by 0.0%.
Report is 2 commits behind head on master.
The diff coverage is 95.4%.

@@           Coverage Diff           @@
##           master   #32718   +/-   ##
=======================================
  Coverage    81.9%    82.0%           
=======================================
  Files         784      784           
  Lines      211004   211002    -2     
=======================================
+ Hits       173012   173022   +10     
+ Misses      37992    37980   -12