@blockly/block-extension-tooltip doesn't match naming convention

[samelhusseini]

Our own block-extension (@blockly/block-extension-tooltip) doesn't abide by the naming convention on: https://developers.google.com/blockly/guides/plugins/naming

Options are:

• Change the naming convention for block (since it's early enough), and before we showcase this at the summit.
• Other reasons for changing the name convention from @blockly/extension-* to @blockly/block-extension is to reduce overload of the word extension as it's very synonymous with plugin and it's not obvious what the difference between @blockly/extension-* and @blockly/plugin-* is.
• Ignore, and new plugins can use the current convention.
• Re-publish the plugin under @blockly/extension-tooltip, deprecating the old one.