Internalize generated ANTLR sources

[alancai98]

Relevant Issues

• Closes Internalize ANTLR-generated parser sources #1446.

Description

• Moves ANTLR-generated sources under internal namespace
  • Updates corresponding code
• Adds filter to API compatibility checker to exclude code under internal namespace
• Adds a comment to partiql-parser README that the ANTLR-generated sources are not to be used outside of code within this package.

Other Information

• Updated Unreleased Section in CHANGELOG: [NO]

  • No, on v1 branch.

• Any backward-incompatible changes? [YES]

  • Moves the public ANTLR-generated sources under the internal namespace. We did not intend for these be used by external consumers of partiql-parser.

• Any new external dependencies? [NO]

• Do your changes comply with the Contributing Guidelines
  and Code Style Guidelines? [YES]

License Information

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

Conformance comparison report-Cross Engine

	Base (legacy)	eval	+/-
% Passing	92.51%	90.70%	-1.80%
✅ Passing	5382	5278	-104
❌ Failing	436	541	105
🔶 Ignored	0	0	0
Total Tests	5818	5819	1
Number passing in both: 5071

Number failing in both: 229

Number passing in legacy engine but fail in eval engine: 312

Number failing in legacy engine but pass in eval engine: 207
⁉️ CONFORMANCE REPORT REGRESSION DETECTED ⁉️
The complete list can be found in GitHub CI summary, either from Step Summary or in the Artifact.
207 test(s) were failing in legacy but now pass in eval. Before merging, confirm they are intended to pass.
The complete list can be found in GitHub CI summary, either from Step Summary or in the Artifact.

Conformance comparison report-Cross Commit-LEGACY

	Base (23f6fee)	4219bb3	+/-
% Passing	92.51%	92.51%	0.00%
✅ Passing	5382	5382	0
❌ Failing	436	436	0
🔶 Ignored	0	0	0
Total Tests	5818	5818	0
Number passing in both: 5382

Number failing in both: 436

Number passing in Base (23f6fee) but now fail: 0

Number failing in Base (23f6fee) but now pass: 0

Conformance comparison report-Cross Commit-EVAL

	Base (23f6fee)	4219bb3	+/-
% Passing	90.70%	90.70%	0.00%
✅ Passing	5278	5278	0
❌ Failing	541	541	0
🔶 Ignored	0	0	0
Total Tests	5819	5819	0
Number passing in both: 5278

Number failing in both: 541

Number passing in Base (23f6fee) but now fail: 1

Number failing in Base (23f6fee) but now pass: 1
⁉️ CONFORMANCE REPORT REGRESSION DETECTED ⁉️. The following test(s) were previously passing but now fail:

Click here to see

• Example 6 — Value Coercion, compileOption: LEGACY

The following test(s) were previously failing but now pass. Before merging, confirm they are intended to pass:

Click here to see

• Example 6 — Value Coercion, compileOption: LEGACY

[yliuuuu]

PR looks good to me, just one nit comment.

[yliuuuu]

Look good to me.