Move src/bin/pg_verifybackup/parse_manifest.c into src/common.

This makes it possible for the code to be easily reused by other
client-side tools, and/or by the server.

Patch by me. Review of this patch in particular by at least Peter
Eisentraut; reviewers for the patch series in general include Dilip
Kumar, Andres Fruend, David Steele, Álvaro Herrera, and Jakub Wartak.

Discussion: http://postgr.es/m/CA+TgmoZ6UGZVnSy5iak6s6+AXu_DewXovDjhLs3-su6nmU_x_g@mail.gmail.com

src/include/common/parse_manifest.h

@@ -0,0 +1,46 @@
+/*-------------------------------------------------------------------------
+ *
+ * parse_manifest.h
+ *	  Parse a backup manifest in JSON format.
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/common/parse_manifest.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef PARSE_MANIFEST_H
+#define PARSE_MANIFEST_H
+
+#include "access/xlogdefs.h"
+#include "common/checksum_helper.h"
+#include "mb/pg_wchar.h"
+
+struct JsonManifestParseContext;
+typedef struct JsonManifestParseContext JsonManifestParseContext;
+
+typedef void (*json_manifest_per_file_callback) (JsonManifestParseContext *,
+												 char *pathname,
+												 size_t size, pg_checksum_type checksum_type,
+												 int checksum_length, uint8 *checksum_payload);
+typedef void (*json_manifest_per_wal_range_callback) (JsonManifestParseContext *,
+													  TimeLineID tli,
+													  XLogRecPtr start_lsn, XLogRecPtr end_lsn);
+typedef void (*json_manifest_error_callback) (JsonManifestParseContext *,
+											  const char *fmt,...) pg_attribute_printf(2, 3)
+			pg_attribute_noreturn();
+
+struct JsonManifestParseContext
+{
+	void	   *private_data;
+	json_manifest_per_file_callback per_file_cb;
+	json_manifest_per_wal_range_callback per_wal_range_cb;
+	json_manifest_error_callback error_cb;
+};
+
+extern void json_parse_manifest(JsonManifestParseContext *context,
+								char *buffer, size_t size);
+
+#endif