refactor: move dynamic import resolution to unit initialization

[Xor-el]

Summary

Move dynamic library symbol resolution (dlopen/dlsym) from lazy
per-call resolution to one-time unit initialization for ARM hardware
capability detection on Linux, Android, BSD, and macOS (Darwin).

Changes

HlpArmHwCapProvider.pas (Linux/Android and BSD)

• Renamed ResolveOnce to ResolveDynamicImports and removed the
  manual FResolved boolean guard, since the initialization section
  guarantees single execution.
• Removed ResolveOnce calls from GetHwCap and GetHwCap2 — the
  function pointers are already resolved by the time any caller can
  reach them.
• Added an initialization section that calls
  ResolveDynamicImports at unit load time.
• Relaxed visibility from strict private to private so the
  initialization section can access the method.

HlpDarwinSysCtl.pas (macOS/iOS)

• Same refactor: renamed ResolveOnce to ResolveDynamicImports,
  removed the FResolved guard, removed the call from HasFeature,
  and moved resolution to an initialization section.

Rationale

The previous pattern resolved imports lazily on first use with a
boolean guard. This worked but added a branch to every call of
GetHwCap, GetHwCap2, and HasFeature. Since these function
pointers never change after resolution, performing the dlopen/dlsym
once at unit initialization is simpler, removes the redundant flag
field, and eliminates repeated nil-check overhead on the hot path.