Hide block count for apps that have no requirement
always hide block count if infinity
add some unit test coverage
Merge pull request #589 from code-dot-org/hideBlockCount

[Finishes #69854942] Hide block count for apps that have no requirement
[Finishes #71443508] stepping through while loop
comment update
Merge pull request #591 from code-dot-org/loopStep

[Finishes #71443508] stepping through while loop
undeletable blocks, disable neighbor bumping
Imported from blockly-core
Merge pull request #592 from code-dot-org/jigsawBugs

[Finishes #70791820, #71629086] undeletable blocks, disable neighbor bumping
Imported from blockly-core
merge