feat: allow injection of httpx client

[silentworks]

What kind of change does this PR introduce?

Allow developers to supply their own httpx client

What is the current behavior?

Httpx client isn't very configurable and has limited options available for the developer

What is the new behavior?

Httpx client can now be configured by the developer and be supplied to the storage library

Additional context

Add any other context or screenshots.

[coveralls]

Pull Request Test Coverage Report for Build 15702426998

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 45 of 49 (91.84%) changed or added relevant lines in 7 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-1.0%) to 96.645%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
storage3/_async/client.py	13	15	86.67%
storage3/_sync/client.py	15	17	88.24%

Files with Coverage Reduction	New Missed Lines	%
storage3/init.py	3	84.21%

Totals
Change from base Build 15702295064:	-1.0%
Covered Lines:	605
Relevant Lines:	626

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💛 - Coveralls