Switch bp2build mutator to bottom up

This should be no-op, as the underlying mutator has not changed yet.

Some other refactoring is required and done in this CL:

- Delete some old, dead ApiBp2build code
- Fix casting to TopDownMutator when it's not necessary

This change is required to prepare for allowlist v2 work, as only
BottomUp mutators can AddDependency.

Bug: 285631638
Test: m nothing
Test: presubmits
Change-Id: I5212a5f5634cc13056195783e6df37ff8eb000da

cc/cc.go

@@ -4273,24 +4273,6 @@ func (c *Module) ConvertWithBp2build(ctx android.Bp2buildMutatorContext) {
 	}
 }
 
-var _ android.ApiProvider = (*Module)(nil)
-
-func (c *Module) ConvertWithApiBp2build(ctx android.TopDownMutatorContext) {
-	if c.IsPrebuilt() {
-		return
-	}
-	switch c.typ() {
-	case fullLibrary:
-		apiContributionBp2Build(ctx, c)
-	case sharedLibrary:
-		apiContributionBp2Build(ctx, c)
-	case headerLibrary:
-		// Aggressively generate api targets for all header modules
-		// This is necessary since the header module does not know if it is a dep of API surface stub library
-		apiLibraryHeadersBp2Build(ctx, c)
-	}
-}
-
 // Defaults
 type Defaults struct {
 	android.ModuleBase