Update to matrix-appservice-bridge 3.x

Update to matrix-appservice-bridge 3.x.

• https://github.com/matrix-org/matrix-appservice-bridge/blob/develop/CHANGELOG.md#300-2021-09-09
• https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/3.0.0-rc1

Todo

• The tests seem to pass npm run mocha -- modules/matrix-bridge/test
• Replace intent.getClient() usage with either Intent functions, or Intent.matrixClient
  • Old client: https://github.com/matrix-org/matrix-js-sdk/blob/b1d239b292b1d6120934c60a25cc9b88ac7fcea2/src/client.ts
  • New client: https://github.com/turt2live/matrix-bot-sdk/blob/03b8b2437daddd5b3c2a2401a25c92ad65befa7d/src/MatrixClient.ts
• Fix intent error handling, search for try { in modules\matrix-bridge
  • Previously in matrix-appservice-bridge@2.x, intent errors would be MatrixError which had errcode fields directly on the object.Now in matrix-appserice-bridge@3.x which uses matrix-bot-sdk, it throws full request responses for non-200 responses, see https://github.com/turt2live/matrix-bot-sdk/blob/9b2a7abd9e3f794e65000ab8fd8352ad38b0b562/src/http.ts#L93
• mxcUrlToHttp