Move ScalarValue tests alongside implementation, move from_slice to datafusion_core

[alamb]

Which issue does this PR close?

Closes #2913

Rationale for this change

I am working on #2891 and it was not clear there were existing ScalarValue tests because they were in a different module than their implementation

Implementation: https://github.com/apache/arrow-datafusion/blob/fd64e6f2e5ca5ba8c33c431b75a3ba9441091970/datafusion/common/src/scalar.rs
Tests https://github.com/apache/arrow-datafusion/blob/85ca8be669dc1fbba4b2eefbf99fc2ed1546cc0c/datafusion/core/src/scalar.rs

🤯

What changes are included in this PR?

1. Move ScalarValue tests alongside implementation
2. move from_slice to datafusion_core (as it is used in the ScalarValue implementation)

Are there any user-facing changes?

from_slice is now in the datafusion_core crate (used to be in datafusion_physical_expr crate), but their is a pub use so no existing code needs to be changed (they can still import from_slice from datafusion_physical_expr)

[alamb]

Github makes this look like a massive diff, but it has only about 5 lines of substance

[alamb]

these tests are moved, verbatim. The only change is that this line

    use arrow::{array::*, datatypes::*};

was removed at the direction of the rust compiler as it was no longer used

[andygrove]

Thanks @alamb. The current state was likely a result of the recent refactoring of crates and modules.

[alamb]

cc @comphead this may affect #2893

Would you like me to wait for that to be ready to merge this PR?

[alamb]

@comphead I merged this PR to make progress on other PRs. I will be happy to help rebase #2893 if you have trouble after this.

[ursabot]

Benchmark runs are scheduled for baseline = fb2221c and contender = d8a2f58. d8a2f58 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java