Merged PR's from SteamKit

[LossyDragon]

This is kind of a rolling issue list of PR's over at SteamKit that have been merged or pushed to it.

Not everything below may be applicable to JavaSteam, if they are not, they are removed once it's looked into more.

• WebApi
• PR 1028 (Allow consumers to specify a custom Machine Info Provider)
• PR 1102 (Add extra asserts connection logic)
• PR 1379 (Less allocations in non-utf8 string reads, fix non-utf8 string writes, optimize both with stack / pool alloc)
• PR 1381 (Improve encryption allocations)
• PR 1384 (Reduce allocations)
• PR 1544 (Use HttpClientFactory for websocket connections, add HttpClientPurpose)

[LossyDragon]

Checked off PR 1015 as Java on other platforms allows longer thread names.

[LossyDragon]

Checked off PR 1067 as the fields are nullable already.