[fxfs] Make fshost launch fxfs as a component

This involved removing the fs_switch option and changing the binary path
option into a format option instead.

Bug: 99591
Change-Id: I34a2e4a27bbbe2df1a0cf9fcaec3787f46cd020a
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/678383
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
Reviewed-by: Stephen Demos <sdemos@google.com>
Fuchsia-Auto-Submit: Chris Suter <csuter@google.com>

Author: sutes-work

src/lib/storage/fs_management/cpp/format.cc

@@ -222,6 +222,24 @@ __EXPORT std::string_view DiskFormatString(DiskFormat fs_type) {
   return format->name().c_str();
 }
 
+__EXPORT DiskFormat DiskFormatFromString(std::string_view str) {
+  static auto* formats = [] {
+    auto* formats = new std::unordered_map<std::string_view, DiskFormat>();
+    for (auto format : {kDiskFormatGpt, kDiskFormatMbr, kDiskFormatMinfs, kDiskFormatFat,
+                        kDiskFormatBlobfs, kDiskFormatFvm, kDiskFormatZxcrypt, kDiskFormatFactoryfs,
+                        kDiskFormatBlockVerity, kDiskFormatVbmeta, kDiskFormatBootpart,
+                        kDiskFormatFxfs, kDiskFormatF2fs, kDiskFormatNandBroker}) {
+      formats->emplace(DiskFormatString(format), format);
+    }
+    return formats;
+  }();
+  if (auto iter = formats->find(str); iter == formats->end()) {
+    return kDiskFormatUnknown;
+  } else {
+    return iter->second;
+  }
+}
+
 __EXPORT std::string_view DiskFormatComponentUrl(DiskFormat fs_type) {
   switch (fs_type) {
     case kDiskFormatBlobfs:

src/lib/storage/fs_management/cpp/format.h

@@ -36,6 +36,7 @@ enum DiskFormat {
 };
 
 std::string_view DiskFormatString(DiskFormat fs_type);
+DiskFormat DiskFormatFromString(std::string_view str);
 
 // Get the component url for the disk format, if it's known. If it's not known, this returns an
 // empty string.