Revert "[Fuchsia] Move args from build/config/fuchsia to gn-sdk"

This reverts commit 66f2206c9bcbcc96f6efa88a0793f769c877a959.

Reason for revert: break webrtc

Original change's description:
> [Fuchsia] Move args from build/config/fuchsia to gn-sdk
>
> They are not overridden by chromium and should be removed from
> declare_args(). Meanwhile gn-sdk should maintain its own copies
> as these parameters are only used there.
>
> To avoid breaking other repos, now the ones in the gn-sdk are
> protected by if-conditions.
>
> Cq-Include-Trybots: luci.chrome.try:fuchsia-smoke-sherlock;luci.chromium.try:fuchsia-arm64-cast-receiver-rel
> Bug: 359657446
> Change-Id: I2b5c8e933ddaf020f23c90692917ad9a5825ff85
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5807393
> Reviewed-by: David Song <wintermelons@google.com>
> Commit-Queue: Zijie He <zijiehe@google.com>
> Cr-Commit-Position: refs/heads/main@{#1347792}

Bug: 359657446
Change-Id: I7c3e85c83d88cd2315619bf36b05fa2a32fc8a4f
Cq-Include-Trybots: luci.chrome.try:fuchsia-smoke-sherlock;luci.chromium.try:fuchsia-arm64-cast-receiver-rel
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5823851
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Zijie He <zijiehe@google.com>
Cr-Commit-Position: refs/heads/main@{#1348091}