Refactoring - Remove redundant definition of BuiltinProgram

[Lichtso]

Problem

Continuation of #31324, this PR aims to unify the remaining two built-in program structures into one. With this, two other changes will become possible:

• Using the LoadedPrograms cache for the built-in programs as well, including its usage statistics and feature gate logic.
• Having multiple functions per built-in program and skipping the instruction deserialization and dispatch.

Summary of Changes

• Replaces BuiltinProgram in the program-runtime with Arc<LoadedProgram> which wraps solana_rbpf::vm::BuiltInProgram.
• Adds name string to LoadedProgramType::Builtin
• Registers one function named "entrypoint" in every built-in program.
• Adjusts the runtimes built-ins to use Arc.
• Adjusts the tests and benchmarks.

[codecov]

Codecov Report

Merging #31429 (0667122) into master (fdf7bda) will increase coverage by 0.0%.
The diff coverage is 87.7%.

@@           Coverage Diff            @@
##           master   #31429    +/-   ##
========================================
  Coverage    81.4%    81.4%            
========================================
  Files         731      731            
  Lines      208593   208662    +69     
========================================
+ Hits       169849   169955   +106     
+ Misses      38744    38707    -37