Avoid clearing binary and library caches between KSP rounds

[cushon]

In dropCaches(), KSP previously called publishGlobalModuleStateModificationEvent(),
KaSessionProvider.getInstance(project).clearCaches(), psiManager.dropResolveCaches(),
psiManager.dropPsiCaches(), and KSObjectCacheManager.clear() on each round.

KSP rounds only add newly generated source files to KaSourceModule and do
not mutate binary libraries or dependencies (KaLibraryModule). Calling
publishGlobalModuleStateModificationEvent() forces Analysis API and FIR
to discard all binary/library symbol provider and Java class caches, which then
have to be recomputed from scratch in every subsequent round.

Switching to publishGlobalSourceModuleStateModificationEvent() preserves
library caches across rounds while properly invalidating source module caches.
Additionally:

• KaSessionProvider.getInstance(project).clearCaches() is redundant because
  KaSessionProvider already subscribes to KotlinModificationEvent and
  clears caches when modification events are published.
• psiManager.dropResolveCaches() is redundant because
  psiManager.dropPsiCaches() already calls dropResolveCaches().

[cushon]

There's some more context including benchmark results in internal bug b/567808367, I am seeing a ~9% wall time improvement for one large KSP action from this.

[jaschdoc]

Thanks for the PR. Reducing the number of manual calls is a good idea. Before I approve, I just want to ask @hfmehmed, do you see any problems with not clearing library caches in KMP setups? If we have commonMain and a terminal compilation task, how does KSP run now? Is processing run on commonMain first and its sources and generated sources available to the terminal compilation task as a library?