V1 release with multiple namespace support

[zengin]

We have gone through the diff with @MIchaelMainer and the diff looks good. The output compiles.

Changes

• Support for multiple namespaces
• Support for nested folder structure for namespaces. This meant modified rules for copy operation.
  • At the time of copy, we clean the old generated files so that we can catch deletions in the diffs. We can't delete whole folders, because there are hand-crafted files in the "extensions" folders even though we have generated files in those folders as well. We are excluding these hand-crafted files from the deletion, we also added a warning into PR template for future additions that are not coming from code generation pipeline.
  • Azure pipeline clears all generated and extensions directories except for the hand-crafted files. It then copies at the top level (com/ folder level) preserving the full generated directory structure.
• Types from options.* namespaces are using fully qualified names inline, and all options.* style imports are removed.
• Camel case naming from the fix here: Bugfix/java import keyword MSGraph-SDK-Code-Generator#274

ColumnDefinition.java -> msgraphBoolean
ContentTypeOrder.java -> msgraphDefault
PersonType.java -> msgraphClass
RemoteItem.java -> msgraphPackage
WorkbookWorksheetProtection.java -> msgraphProtected

• TeamCloneBody.java and UserGetMailTipsBody.java seem to have double imports on java.util.EnumSet. This is not a blocking issue.

Note on breaking changes

• Namespace changes don't look breaking, however the fixes from Bugfix/java import keyword MSGraph-SDK-Code-Generator#274 are changing the type names. So after checking this in, we will hold off the release to bundle it with other breaking changes to have one major bump in release number. (cc: @baywet)

Related work items

AB#5033
AB#5032
AB#5031

[baywet]

@zengin thanks! I've renamed the milestone from 1.10.0 to 2.0.0 and pushed it another week to give us headway to close the other issues (potentially breaking) in there.