[1.x] Fixed setting attributes in reviewSubgraph

[samskalicky]

Description

Fixed bugs introduced in #18779:

• prevents setting attributes on subgraph ops
• getting the subgraph string from a const Graph object
• setting tensors on param nodes, maps from subgraph input names to top level graph names
• added support for escaping quotes \" when parsing strings in json
• adding new nodes in graph pass
• aligned string allocation to match free (was new changed to malloc)

[mxnet-bot]

Hey @samskalicky , Thanks for submitting the PR
All tests are already queued to run once. If tests fail, you can trigger one or more tests again with the following commands:

• To trigger all jobs: @mxnet-bot run ci [all]
• To trigger specific jobs: @mxnet-bot run ci [job1, job2]

---

CI supported jobs: [miscellaneous, windows-cpu, edge, windows-gpu, unix-cpu, unix-gpu, sanity, website, centos-cpu, centos-gpu, clang]

---

Note:
Only following 3 categories can trigger CI :PR Author, MXNet Committer, Jenkins Admin.
All CI tests must pass before the PR can be merged.

[sandeep-krishnamurthy]

@mseth10 @waytrue17 can you please help review. Thanks.

[access2rohit]

LGTM!