json: fix parsing json problems when json config is invalid.

Add parsing json as invalid cases:
1.json content that not enclosed in {}, it should be parsed as invalid, e.g.

"abc":"not encloesed in

json: fix parsing json problems when json config is invalid.

Add parsing json as invalid cases:
1.json content that not enclosed in {}, it should be parsed as invalid, e.g.

"abc":"not encloesed in {}"

2.json content that 'subsystems' not associate with array, it will report error and return failure, e.g.

{"subsystems":"123"}

3.handle other invalid json formats, report and return failure, e.g. duplicate keys.

Added `spdk_json_find` API return errcode: EPROTOTYPE - json not enclosed in {}.

json config with content:
1."not enclosed in {}"
2."'subsystems' not be an array"
3."duplicate key in json"
and some other invaild cases will be regarded as invalid json config, and will fail to start app.

Fixes #2599

Signed-off-by: tongkunkun <tongkunkun_yewu@cmss.chinamobile.com>
Change-Id: I02574c9acd7671e336d4c589ebbff8ed21eb3681
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/13754
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: GangCao <gang.cao@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@nvidia.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

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