skip importing CondaPkg if not needed (take 3)

[cjdoris]

Simpler approach to #768

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	bb4a530...	main / bb4a530...
basic/@py/pydict/init	0.254 ± 0.048 ms	0.238 ± 0.049 ms	1.07 ± 0.3
basic/@py/pydict/pydel	0.249 ± 0.033 ms	0.238 ± 0.022 ms	1.05 ± 0.17
basic/julia/pydict/init	0.214 ± 0.069 ms	0.223 ± 0.064 ms	0.961 ± 0.41
basic/julia/pydict/pydel	0.229 ± 0.033 ms	0.21 ± 0.021 ms	1.09 ± 0.19
gc/full	0.579 ± 0.02 s	0.601 ± 0.0093 s	0.964 ± 0.036
time_to_load	2.09 ± 0.05 s	2.02 ± 0.015 s	1.03 ± 0.026

Memory benchmarks

	main	bb4a530...	main / bb4a530...
basic/@py/pydict/init	5.01 k allocs: 0.0764 MB	1 k allocs: 15.7 kB	5
basic/@py/pydict/pydel	5.01 k allocs: 0.0764 MB	2 allocs: 32 B	2.5e+03
basic/julia/pydict/init	4.01 k allocs: 0.0612 MB	4.01 k allocs: 0.0612 MB	1
basic/julia/pydict/pydel	4.01 k allocs: 0.0612 MB	10 allocs: 0.188 kB	334
gc/full	0 allocs: 0 B	0 allocs: 0 B
time_to_load	0.143 k allocs: 10.6 kB	0.143 k allocs: 10.6 kB	1

[cjdoris]

@JamesWrigley how about this version? I don't think the getpref stuff needs to be made more complicated just for this one purpose, so this uses @load_preference directly.

I also removed the loading of Pkg from JuliaCall too - it was only loaded to activate the correct project, but instead I've changed it to use --project to start Julia in the correct project.

[JamesWrigley]

Thank you very much for getting that over the line :) Out of curiosity, when do you plan the next release?

[cjdoris]

I've just merged a flurry of bugfixes so I'll get a release out now.