Update ESP-IDF for I2C controller and target fixes

[floitsch]

Update third_party/esp-idf from 1d89388f11383182b35c06fe44278847235b3a53 to bf81d4c8cdaeaee5a13feca0c8aea60988f12807, incorporating two merged I2C fixes:

• toitware/esp-idf#134: drain the controller TX FIFO before a repeated START so the next address cannot overwrite pending write data.
• toitware/esp-idf#135: refresh the target RX FIFO count between interrupt causes, preventing a 20-byte write from being reported as 40 bytes with a corrupt suffix. Includes a deterministic two-device Unity regression.

This is the standalone SDK update for #3240 and #3241. Their PR diffs do not change the ESP-IDF submodule.

Validation: the merged controller source is identical to the revision covered by #3240's 19-size, two-frequency hardware regression. The merged target source and test app are identical to the version validated with the Unity hardware A/B: unpatched fails with Expected 20 Was 40, fixed passes all three payloads on both boards. Verified the SDK range contains only these two merged fixes and that this PR changes only the submodule pointer; git diff --check passes. No additional hardware run was performed for this pointer-only update.