Use julia --project in JuliaRunner

[etpinard]

Currently the JuliaRunner spawns a Dash.jl server using the julia executable with no option. This means the JuliaRunner expects the Julia test dependencies to be installed in the default environment, located e.g. in ~/.julia/environments/v1.9/.

While installing the Julia test dependencies in the default environment might be ok in a test container, it is not the recommended way to develop Julia packages.

Using the julia --project in the server-spawning command, makes the JuliaRunner use the test dependencies from the Dash.jl package environment, the same test dependencies we used in the Dash.jl unit tests.

Contributor Checklist

• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community

[alexcjohnson]

💃 Please add a changelog entry and we'll merge :)