refactor(rpc): change 'connected_duration' duration unit to milliseconds

[chanhsu001]

What problem does this PR solve?

make duration unit consistent in get_peers RPC

Problem Summary:

What is changed and how it works?

Proposal: in 'get_peer' RPC, connected_duration uses secs but last_ping_duration uses millis, we need to change connected_duration uses millis.

What's Changed:

Related changes

• PR to update owner/repo:
• Need to cherry-pick to the release branch

Check List

Tests

• Unit test

Side effects

• rpc client should change 'connected_duration' duration unit from 'second' to 'millisecond' when get_peers RPC is used.

Release note

**BREAKING RPC**. Change field `connected_duration` time unit from seconds to **milliseconds** in `get_peers` RPC to make time unit  used  consistently in `get_peers` , RPC clients are suggested to modify time quantity correspond with this change.

[doitian]

This is a breaking change, please add the release note.

[chanhsu001]

This is a breaking change, please add the release note.

i already add a note at end of PR content, is it ok?

[doitian]

This is a breaking change, please add the release note.

i already add a note at end of PR content, is it ok?

We'll use the content inside the release note to generate the CHANGELOG.

fix(rpc): foo foo #3028

```release-note
bar bar
```

Will generate an entry like this:

- #3028: fix(rpc): foo foo

    bar bar

[bors]

This PR was included in a batch that successfully built, but then failed to merge into develop. It will not be retried.

Additional information:

{"message":"At least 2 approving reviews are required by reviewers with write access.","documentation_url":"https://docs.github.com/articles/about-protected-branches"}

[quake]

bors r=quake,doitian

[bors]

Build succeeded:

• ci