feat: command batching SOFIE-2549

[Julusian]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

feature

• What is the current behavior? (You can also link to an open issue here)

When sending commands to the atem, it is only possible to send one per packet.

• What is the new behavior (if this is a feature change)?

The sendCommands method is now exposed, allowing for sending multiple commands in one packet.
Each call to the method will result in packets being sent, no buffering/debouncing is performed between calls. Commands are packed into packets in order, up to a defined byte limit per packet.

The maximum packet size is defined based on the packetMtu property supplied to the constructor. Care should be taken when setting this, as any upload transfers do not fully respect this value and will result in packets failing to send.

• Other information:

This partially covers #140, but only solves the case of constructing the commands manually (or with atem-state), not usage through the methods provided on the Atem class.
A friendlier batching api can be built on top of this work by someone later.

I have tested this against a Constellation 2ME HD by sending a pair of MixEffectKeyDVECommand commands multiple time at once, enough so that it spans multiple packets. The packets were acked, indicating that they were transmitted and received successfully.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (9f87cc1) 86.29% compared to head (fc1256e) 86.38%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
src/atem.ts	95.00%	1 Missing ⚠️
src/lib/atemSocket.ts	94.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   86.29%   86.38%   +0.09%     
==========================================
  Files         180      181       +1     
  Lines        5814     5853      +39     
  Branches      958      965       +7     
==========================================
+ Hits         5017     5056      +39     
  Misses        775      775              
  Partials       22       22              

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[nytamin]

Looks good to me from an initial read through