feat: added map method to query builders

[akorchyn]

• added map method to change the query result type if you want to construct it some other way around. These methods help to simplify mapping internally (more clean) and provide a big improvement in dev UX on fetching data.

• Bug-fixed Delegation::view_balance method that returned staked balance instead of unstaked.

@race-of-sloths

[race-of-sloths]

@akorchyn Thank you for your contribution! Your pull request is now a part of the Race of Sloths!
We are launching a survey "Who is faster? You vs SpaceX"

Current status: waiting for scoring

We're waiting for maintainer to score this pull request with @race-of-sloths score [0,1,2,3,5,8,13] command. Alternatively, autoscoring [1,2] will be applied for this pull request

What is the Race of Sloths

Race of Sloths is a friendly competition where you can participate in challenges and compete with other open-source contributors within your normal workflow

For contributors:

• Tag @race-of-sloths inside your pull requests
• Wait for the maintainer to review and score your pull request
• Check out your position in the Leaderboard
• Keep weekly and monthly streaks to reach higher positions
• Boast your contributions with a dynamic picture of your Profile

For maintainers:

• Score pull requests that participate in the Race of Sloths and receive a reward
• Engage contributors with fair scoring and fast responses so they keep their streaks
• Promote the Race to the point where the Race starts promoting you
• Grow the community of your contributors

Feel free to check our website for additional details!

Bot commands

• For contributors
  • Include a PR: @race-of-sloths include to enter the Race with your PR
• For maintainers:
  • Invite contributor @race-of-sloths invite to invite the contributor to participate in a race or include it, if it's already a runner.
  • Assign points: @race-of-sloths score [1/2/3/5/8/13] to award points based on your assessment.
  • Reject this PR: @race-of-sloths exclude to send this PR back to the drawing board.
  • Exclude repo: @race-of-sloths pause to stop bot activity in this repo until @race-of-sloths unpause command is called

[dj8yfo]

this thingy here has to test the same thing that will be published
RUSTDOCFLAGS="-D warnings" cargo doc --all-features --document-private-items

https://github.com/near/near-api-rs/blob/main/.github/workflows/test.yml#L43

[akorchyn]

this thingy here has to test the same thing that will be published RUSTDOCFLAGS="-D warnings" cargo doc --all-features --document-private-items

https://github.com/near/near-api-rs/blob/main/.github/workflows/test.yml#L43

Don't think it related to this PR, though