Support trimmed variant build in soong

variable.go:
add a new product variable TrimmedApex which is controlled by
environment variable PRODUCT_TRIMMED_APEX

config.go:
all config to check if trimmed build is turned on or not

apex.go:
add overridable apex module property:
use_DCLA: <DCLA apex module>

"use_DCLA" allows user to just use the lib list in DCLA to determine
which native shared libraries to trim. This property is no-op if
TrimApexEnabled is set to false.

builder.go
1, if it is to produce a trimmed variant, fix the default version code
by making the last variant digit to 2. this is only useful in local
build. in production build, there is apex manifest injection by
coastguard that determines the actual version code.

2, create a new apex rule called: "TrimmedApexRule", this rule invokes
an apexer wrapper called apexer_with_trim_preprocessing which will
properly trim the target libs.

BUG: b/259381334
TEST: adbd banchan build for both static and trimmed variant
Change-Id: I38a91cdef86a3c9185d00610ab3dd7acd07fd90a

android/variable.go

@@ -380,6 +380,7 @@ type productVariables struct {
 
 	Ndk_abis *bool `json:",omitempty"`
 
+	TrimmedApex                  *bool `json:",omitempty"`
 	Flatten_apex                 *bool `json:",omitempty"`
 	ForceApexSymlinkOptimization *bool `json:",omitempty"`
 	CompressedApex               *bool `json:",omitempty"`
@@ -502,6 +503,7 @@ func (v *productVariables) SetDefaultConfig() {
 		Malloc_zero_contents:         boolPtr(true),
 		Malloc_pattern_fill_contents: boolPtr(false),
 		Safestack:                    boolPtr(false),
+		TrimmedApex:                  boolPtr(false),
 
 		BootJars:     ConfiguredJarList{apexes: []string{}, jars: []string{}},
 		ApexBootJars: ConfiguredJarList{apexes: []string{}, jars: []string{}},