Feature - Enable Program-Runtime-v2 and Loader-v4

[Lichtso]

Problem

The loader-v4 is currently unreachable outside of unit tests. So, a feature gate for local testing should be introduced.

Summary of Changes

• Adds a new feature enable_program_runtime_v2_and_loader_v4.
• Adds a feature gated BuiltinPrototype for the solana_loader_v4_program.

Feature Gate Issue: #33293

[dmakarov]

LGTM, except it seems that program runtime v2 and loader v4 is the same thing (at least gated by the same feature flag), is that so?

[Lichtso]

Yes, the loader-v4 is the only entrypoint to the program-runtime-v2 and program-runtime-v2 is only reachable from the loader-v4. While they are not the same thing, there is still a correlation.

[codecov]

Codecov Report

Merging #33294 (ac2e997) into master (86dd18b) will increase coverage by 0.0%.
Report is 2 commits behind head on master.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##           master   #33294   +/-   ##
=======================================
  Coverage    81.9%    81.9%           
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  Files         793      793           
  Lines      214812   214813    +1     
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+ Hits       176092   176095    +3     
+ Misses      38720    38718    -2