Add an ID generator in preparation for PR 2885

[avantgardnerio]

Which issue does this PR close?

Closes #2886.

Rationale for this change

Need a way to generate unique identifiers to alias subqueries while optimizing.

What changes are included in this PR?

Making the OptimizerConfig mutable and adding a next_id() function.

Are there any user-facing changes?

No.

[codecov-commenter]

Codecov Report

Merging #2887 (9442f07) into master (5a63c87) will decrease coverage by 0.00%.
The diff coverage is 82.35%.

❗ Current head 9442f07 differs from pull request most recent head ec77e2d. Consider uploading reports for the commit ec77e2d to get more accurate results

@@            Coverage Diff             @@
##           master    #2887      +/-   ##
==========================================
- Coverage   85.35%   85.34%   -0.01%     
==========================================
  Files         276      276              
  Lines       49290    49294       +4     
==========================================
- Hits        42070    42069       -1     
- Misses       7220     7225       +5     

Impacted Files	Coverage Δ
datafusion/core/tests/user_defined_plan.rs	87.79% <ø> (ø)
datafusion/optimizer/src/optimizer.rs	75.00% <0.00%> (-13.24%)	⬇️
datafusion/optimizer/src/utils.rs	88.57% <ø> (ø)
datafusion/core/src/execution/context.rs	78.82% <100.00%> (+0.02%)	⬆️
...tafusion/optimizer/src/common_subexpr_eliminate.rs	94.11% <100.00%> (ø)
datafusion/optimizer/src/eliminate_filter.rs	100.00% <100.00%> (ø)
datafusion/optimizer/src/eliminate_limit.rs	100.00% <100.00%> (ø)
datafusion/optimizer/src/filter_null_join_keys.rs	92.85% <100.00%> (ø)
datafusion/optimizer/src/filter_push_down.rs	98.23% <100.00%> (ø)
datafusion/optimizer/src/limit_push_down.rs	99.67% <100.00%> (ø)
... and 7 more

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[ursabot]

Benchmark runs are scheduled for baseline = eed77a2 and contender = 6a5de4f. 6a5de4f 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