[v4] break: rename all interfaces to drop 'I' prefix

[adidahiya]

Changes proposed in this pull request:

Drop the I prefix from all interface names.

• In general, the TypeScript community has moved away from this code style and it is not recommended in the TypeScript Handbook (they used to have even more opinionated docs there telling you never to prefix your interfaces). It is a holdover from C#/.NET code style and has largely been deemed unnecessary in TypeScript. See Microsoft/TypeScript-Handbook#121.
• typescript-eslint removed it from its recommended rules a while ago, indicating that the linting community prefers not to use TSLint’s original (very old) default of enforcing the prefix code style.
• Further arguments in this StackOverflow post.

Other related changes in this refactor as a result of the renames:

• KeyCombo disambiguated from the interface. The component is now KeyComboTag (it looks kind of like a Tag component)
• Toaster disambiguated from the interface. The interface is now ToasterInstance.
• TreeNode disambiguated from the interface. The interface is now TreeNodeInfo.
• LocatorImpl / Locator disambiguation
• MenuContextImpl / MenuContext disambiguation

[blueprint-bot]

fix tests

Previews: documentation | landing | table

[blueprint-bot]

fix select tests

Previews: documentation | landing | table

[blueprint-bot]

fix tests type checking

Previews: documentation | landing | table

[blueprint-bot]

fix panel typo

Previews: documentation | landing | table

[blueprint-bot]

update interface name references in docs

Previews: documentation | landing | table