[MG_Backend] (DirectGLES): the monolith client-array snapshot compiles in every flavor

The indexed and indirect client-memory upload added by 62bfe461 landed inside
`#if MOBILEGL_BUILD_DISAGGREGATED`, and that guard was wrong in the one way a
guard can be wrong without a test saying so: the code exists FOR the monolith
arm - every entry point in the family early-returns when `MG_Config::Transport
!= Monolith` - and the monolith arm is what the pull, verify and push builds
run, not a split-arm fallback. Only the split lane was building the change, so
only the split lane could compile it.

Both CI jobs that build without MOBILEGL_BUILD_DISAGGREGATED were red on the
same twenty diagnostics: `build explicit pull runtime control` (the pull
library retrace's monolith control measures) and `build-linux-verify`
(MOBILEGL_PIPE_VERIFY=ON). DirectGLES.cpp:8437/8455/8521/8537 are the two
indirect executors and :9225/9251/9623/9637/9675/9700 the indexed family,
every one of them in an entry point that compiles in all four flavors, calling
names the pull build had no declaration for:

  error: no member named 'SyncClientSideVertexArraysForIndirectFetch' in
  namespace 'MobileGL::MG_Backend::DirectGLES::VertexArrayImpl'
  ... and SyncClientSideVertexArraysForIndexedFetch, likewise.

The block moves out of the guard rather than being duplicated per flavor, so
the split build's preprocessed text and behaviour are unchanged: the three
wrappers keep their `Transport != Monolith` early return, and in the
transport-free flavors that comparison folds to a compile-time false
(Config.h:566) exactly as it does in every other monolith-only body in this
file.

What the guard also covered, and moves with it:

  * ClientFetchPlan.h - no longer behind `MOBILEGL_BUILD_DISAGGREGATED &&
    MOBILEGL_PIPE_PUSH`. The plan IS the monolith arm's arithmetic (the file's
    own header says so: "the monolith arm asks it to size the per-draw upload"),
    so a pull build that cannot see it cannot answer the question.
  * BackendVertexArrayObject::SyncClientSideAttributesForDraw - declaration and
    definition, the callee of SyncClientSideVertexArraysForFetch.
  * The `#include <MG_Impl/Pipe/ClientFetchPlan.h>` in Managers.h, which had
    been inside the same `#if MOBILEGL_PIPE_PUSH` as the two P3a/P4a includes
    it was appended to.

G1: the three wrappers and the byte reader take internal linkage (`static`),
the spelling the sibling SyncClientSideVertexArraysForDrawArrays already uses
at DirectGLES.cpp:2422 for exactly this reason. Verified on the pull build
(Release/INFO, LTO off, library target only, the monolith-symbol-report job's
own flags): 0 added / 0 removed / 0 resized / 0 renamed, .text +0, and every
one of the new names is LOCAL (`t`/`b`) with 0 of them in the dynamic table.
Had they kept external linkage they would have been 0 in the pull symbol delta
anyway (CXX_VISIBILITY_PRESET hidden) and 4 in a Debug build's dynamic table,
which is the configuration CMakeLists.txt:629-641 switches to `default`.

Verified: build-pull rc=0, build-push rc=0, build-verify
(MOBILEGL_PIPE_VERIFY=ON, DISAGGREGATED=OFF) rc=0, build-split rc=0; split
regressions green under both MOBILEGL_TRANSPORT=monolith and =inproc for
ClientVertexArrayScenario (18/18 each) and DrawRangeElements|MultiDraw (119/119
each), so the client-array behaviour 62bfe461..cb64b62b repaired is not
regressed.

MobileGL/MG_Backend/DirectGLES/Managers.cpp

@@ -5545,7 +5545,6 @@ namespace MobileGL::MG_Backend::DirectGLES {
         }
 #endif // MOBILEGL_PIPE_PUSH
 
-#if MOBILEGL_BUILD_DISAGGREGATED
         // THE CLIENT-ARRAY UPLOAD FOR A DRAW WHOSE FETCHED ELEMENTS (first, count) DOES NOT
         // DESCRIBE. SyncClientSideAttributesForDrawArrays below answers the non-indexed family
         // exactly and nothing else: an indexed draw reads the elements its INDICES name, an
@@ -5652,7 +5651,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
             }
             return true;
         }
-#endif
+
         void BackendVertexArrayObject::SyncClientSideAttributesForDrawArrays(
             const SharedPtr<MG_State::GLState::VertexArrayObject>& stateVAOObject, GLint first, GLsizei count,
             Uint32 fetchBaseInstance) {