MXCrypto: Reset OTKs when some IDs are already used

[manuroe]

This is a mitigation for element-hq/element-ios#3721.
But it does not fix the root issue.

This is how this PR behaves on the steps to reproduce:

2020-10-08 09:16:22.890670+0200 Riot[31404:1330203] [MXHTTPClient] #12 - POST _matrix/client/r0/keys/upload/SYNBAYVHFQ completed in 196ms
2020-10-08 09:16:22.891049+0200 Riot[31404:1330203] [MXHTTPClient] Request 0x6000002a2ec0 failed for path: _matrix/client/r0/keys/upload/SYNBAYVHFQ - HTTP code: 400. Error: Error Domain=com.alamofire.error.serialization.response Code=-1011 "Request failed: bad request (400)" UserInfo={NSLocalizedDescription=Request failed: bad request (400), NSErrorFailingURLKey=https://matrix-client.matrix.org/_matrix/client/r0/keys/upload/SYNBAYVHFQ, com.alamofire.serialization.response.error.data={length = 531, bytes = 0x7b226572 72636f64 65223a22 4d5f554e ... 4167277d 7d7d227d }, com.alamofire.serialization.response.error.response=<NSHTTPURLResponse: 0x600001d17e40> { URL: https://matrix-client.matrix.org/_matrix/client/r0/keys/upload/SYNBAYVHFQ } { Status Code: 400, Headers {
2020-10-08 09:16:22.891735+0200 Riot[31404:1330449] [MXCrypto] uploadOneTimeKeys fails.
2020-10-08 09:16:22.891984+0200 Riot[31404:1330449] [MXCrypto] generateAndUploadOneTimeKeys: Failed to publish one-time keys. Error: Error Domain=org.matrix.sdk Code=6 "One time key signed_curve25519:AAAAAQ already exists. Old key: {"key":"mbMSl5/v4ZUOYa4K3WjIdpB/vCEh/gjB4FhSWOq3IAA","signatures":{"@superman:matrix.org":{"ed25519:SYNBAYVHFQ":"CteVb3rbYFQ4qxAqg3YsU7EaUN6tSmZK+OssNU8At0UCD/vQuLuxh21jalNGpn9HvtTNz10Qsw/X5gTYmXVbDQ"}}}; new key: {'key': 'XiwFps8Lz/+VWflVk/1O7P6gz/2q2Z118drmjnzjrTA', 'signatures': {'@superman:matrix.org': {'ed25519:SYNBAYVHFQ': 'BRYhdAJRlE3luwP//29pyuX3DxhJw8WxextbPY6Wg8eL+NMaDQnYixSpLLxuj5AdmnzZhgKxERs3SxsMV+NtAg'}}}" UserInfo={errcode=M_UNKNOWN, httpResponse=<NSHTTPURLResponse: 0x600001d17e40> { URL: https://matrix-client.matrix.org/_matrix/client/r0/keys/upload/SYNBAYVHFQ } { Status Code: 400, Headers {
2020-10-08 09:16:22.896053+0200 Riot[31404:1330449] [MXCrypto] uploadOneTimeKeys: Reset local OTKs because the server does not like them
2020-10-08 09:16:22.896735+0200 Riot[31404:1330449] [MXCrypto] uploadOneTimeKeys: Upload 1 keys
2020-10-08 09:16:22.896911+0200 Riot[31404:1330449] [MXHTTPClient] #13 - POST _matrix/client/r0/keys/upload/SYNBAYVHFQ
2020-10-08 09:16:23.101934+0200 Riot[31404:1330203] [MXHTTPClient] #13 - POST _matrix/client/r0/keys/upload/SYNBAYVHFQ completed in 205ms
2020-10-08 09:16:23.669519+0200 Riot[31404:1330203] [MXHTTPClient] #5 - POST _matrix/client/r0/keys/upload/SYNBAYVHFQ completed in 1992ms
2020-10-08 09:16:23.669972+0200 Riot[31404:1330449] [MXCrypto] uploadDeviceKeys done for @superman:matrix.org:

We detect the problem and we retry with new OTKs

[manuroe]

I double checked code from android and web. We store the OLM account in the same way as other SDKs. I cannot understand how a rotation of OTKs and a reuse of existing IDs can happen.