add {TDigest,ScalarValue,Accumulator}::size

[crepererum]

Which issue does this PR close?

None, but helps with #3940.

Rationale for this change

I need some helper methods to determine in-mem sizes of certain objects.

What changes are included in this PR?

Determine in-mem size of TDigest, ScalarValue, and Accumulator.

Are these changes tested?

-

Are there any user-facing changes?

⚠️ Breaking Change: Accumulator now requires fn size(&self) -> usize;!

[alamb]

I think it looks great -- thank you @crepererum

I had a few suggestions about docstrings but I don't think they are required (we could do them as a follow on PR).

For anyone following along, this is additional foundation to add proper memory accounting to DataFusion so its resource consumption can be constrained.

Note as this PR changes the API I plan to leave it open for at least 24 hours per https://arrow.apache.org/datafusion/contributor-guide/index.html#merging-prs

cc @Dandandan @andygrove @mingmwang @milenkovicm @tustvold and @yjshen

[ursabot]

Benchmark runs are scheduled for baseline = e1204a5 and contender = e015043. e015043 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