Preparation work for 4.29 (2023-09) and open master for development

[MohananRahul]

• Create R4_28_maintenance branch
• Move 4.28-I builds to R4_28_maintenance branch
• Update R4_28 maintenance branch with release version for 4.28+ changes
• Update Parent pom and target sdk deployment jobs for R4_28_maintenance branch
• Create new test jobs for 4.29
• Configure SWT build scripts for 4.29
• Splash Screen for 4.29 (2023-09)
• Create 4.29-I-builds repo
• POM and product version changes for 4.29 release
• Update product version number to 4.29 across build scripts
• Move previous version to 4.28RC2 across build scripts #1102
• Update version number in Mac's Eclipse.app for 4.29
• Disable the freeze report for 4.29
• Clean forceQualifierUpdate files for doc bundles
• Cleanup approved api list
• Update builds and repo cleanup scripts for 4.29 #1123
• Create new I-build job for 4.29 release
• Update check composites script to verify 4.29 repositories
• Update Comparator repo and eclipse run repo to 4.29-I-builds repo #1122
• Version bumps for 4.29 stream #1125
• Update previous release version to 4.28 GA across build scripts
• Update build calendar for platform 4.29 release
• Deploy ecj compiler from 4.28 GA and use it for 4.29 M1 build
• Update generic repos I-builds, Y-builds, P-builds to point to 4.29 repos #1148

For previous issue refer to #912

[MohananRahul]

Deploy ecj compiler from 4.28 GA and use it for 4.29 M1 build:
no change in ecj version 3.34.0.v20230523-1233

[akurtakov]

All subtasks completed.