Support signed declare

[cptartur]

Please check if the PR fulfills these requirements

• [ ] The formatter, linter, and tests all run without an error
• [ ] Tests for the changes have been added (for bug fixes/features)
• [ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Closes #289

This PR doesn't include tests for the new method as it will have to be added once signed declare is actually supported in StarkNet.

• What is the current behavior? (You can also link to an open issue here)

Only unsigned declare is supported

What is the new behavior (if this is a feature change)?

as above

Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

Yes

• transactions module was moved to net
• transactions module is deprecated
• deprecated AccountClient.sign_transaction

Other information

n/a

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (update/cairo-0.10.0@59b7b1a). Click here to learn what that means. The diff coverage is n/a.

:exclamation: Current head e6258c0 differs from pull request most recent head 8e943f2. Consider uploading reports for the commit 8e943f2 to get more accurate results

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