Custom timeout for requests

[ckeshava]

High Level Overview of Change

Certain requests could take more time to return a response, than the default 10 seconds duration. This change allows users to specify a custom timeout parameter to all requests.
Additionally, this PR sets up uniform interfaces for all Client._request_impl overridden functions.

Context of Change

In the present code, all requests are given 10 seconds duration to return a response. Any longer latency results in a timeout. This is inconvenient for certain commands that are known to take up more time, for instance, admin-only commands like the ledger command.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (You added tests for code that already exists, or your new feature included in this PR)
• Documentation Updates
• Release

Did you update CHANGELOG.md?

• Yes
• No, this change does not impact library users

Test Plan

This is an existing integration test that invokes the ledger command at tests/integration/reqs/test_ledger.py. Which other command might take up more time?

[mvadari]

It doesn't look like this PR actually modifies the external-facing methods.

[ledhed2222]

i just happened to see this. it looks good to me! great idea :)

[ckeshava]

thank you for the reviews. If there are no more objections, I'd like to merge this PR