Remove alignment requirements in the EventPipe format

[davidfowl]

The event pipe format requires keeping a position cursor as reading event blob object assumes the data is stored on a 4 byte boundary (https://github.com/Microsoft/perfview/blob/master/src/TraceEvent/EventPipe/EventPipeFormat.md#the-eventblock-object). This requirement is unfortunate and strange for streaming processing, we should figure out if we can get rid of it.

[noahfalk]

The current readers expect certain points in the data to be aligned and would stop working if it wasn't. Which leaves us with two options:

1. Do a format breaking change - stop aligning the data
2. Use encoding tricks when the stream is written so that the implicitly sized padding at the beginning of blocks is always zero-size but the alignment is still correct. The easiest way I see to do this would be to use the blob tag to insert an explicit amount of padding before the block objects begin.

[noahfalk]

The alignment requirements are gone as part of the new NetTrace V6 format.
https://github.com/microsoft/perfview/blob/main/src/TraceEvent/EventPipe/NetTraceFormat.md#simplify-the-streamheader-object-headerfooters-alignment-and-versioning

A parser for the format is already implemented in TraceEvent but we haven't yet committed on it being finalized. E2E scenarios that use it are still under development.