jstz proto: introduce new account

[ryutamago]

Context

first step of migrarting to a new account
task link
in preparation for 255

Description

Added a new account context that handles address of both user and smart function. For a clearer api, we should use SmartFunctionHash for methods that's only intended for sf. This can be implemented after the migration to the new account type is completed.

In the next step, the old account should be replaced with the new one.

Manually testing the PR

Unit tests are added.

[codecov]

Codecov Report

Attention: Patch coverage is 88.63198% with 59 lines in your changes missing coverage. Please review.

Project coverage is 49.21%. Comparing base (345123f) to head (513e63a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/jstz_proto/src/context/new_account.rs	88.80%	23 Missing and 35 partials ⚠️
crates/jstz_proto/src/error.rs	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
crates/jstz_proto/src/error.rs	20.00% <0.00%> (-0.28%)	⬇️
crates/jstz_proto/src/context/new_account.rs	89.11% <88.80%> (-6.02%)	⬇️

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[zcabter]

To aid with review, it would be helpful to add the specific commands that execute your tests in the "Manual Testing" section.

[zcabter]

LGTM overall. Good job. 🚀