Add compressed JSON format for dac_controlset

[Schlepptop]

The current format for the dac_controlset JSON is very space-inefficient. NVS allows for 4000 characters, which is not a lot by itself. Setting a register with {"reg":25,"val": 5}, which is even worsened by the escapes needed to store it (NVS writes {\"reg\":25,\"val\":5}) doesn't help, so I propose supporting this alternative format that uses a single flat array instead.

• Register write:
  [reg, val]
  Writes a single byte value to a register.

• Burst write:
  [reg, [val1, val2, ..., valN]]
  Writes multiple bytes to a register in one burst. The second item must be a JSON array.

• Delay:
  ["d", duration_ms]
  Pauses execution for the specified number of milliseconds.

• Bitwise operations:
  ["&", reg, val] — Read-modify-write: AND value into register
  ["|", reg, val] — Read-modify-write: OR value into register

Notes:

• All entries are parsed in order from the start of the array.
• Invalid formatting or unexpected types will cause the function to return false.
• Only numeric register addresses and values are allowed.

Example input:

     [
        0, 128,
        "d", 50,
        "|", 2, 240,
        "&", 2, 15,
        "g", 22, 0,
        25, [4, 5, 6, 7],
        1, 0
      ]

This will:

• Write 128 to reg 0
• Delay 50ms
• OR 240 into reg 2
• AND 15 into reg 2
• Set GPIO 22 to level 0
• Burst write [4,5,6,7] to reg 25
• Write 0 to reg 1

This is obviously not as simple to write by hand, but easy enough to generate from header files that are supplied by manufacturers.

[gemini-code-assist]

Summary of Changes

Hello @Schlepptop, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly optimizes the storage and parsing of DAC control sequences by introducing a new, highly compressed JSON array format. This change allows for more complex and longer control sequences to be stored within the limited memory constraints of embedded systems, while maintaining compatibility with the existing object-based JSON format. The core functionality now intelligently dispatches to the appropriate parser based on the structure of the provided control set.

Highlights

• New Compressed JSON Format: Introduced a space-efficient, flattened array JSON format for DAC control sequences. This new format supports direct register writes ([reg, val]), burst writes ([reg, [val1, ..., valN]]), delays (["d", duration_ms]), and bitwise AND/OR operations (["&", reg, val] or ["|", reg, val]).
• Dual Format Support: The i2c_json_execute function has been enhanced to intelligently detect and process either the existing object-based JSON control sets or the newly introduced compressed array format, ensuring backward compatibility while enabling the new efficiency.
• Memory Optimization: The primary motivation for this change is to significantly reduce the memory footprint of DAC control sets, which are often stored in Non-Volatile Storage (NVS) with limited capacity. The compressed format addresses the space inefficiency of the previous verbose JSON structure.

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