To big BearSSL::WiFiClientSecure buffer size

[se-fLa]

writePoint failes and often crashes with out of memory on ESP12 device due to big buffer size and possibly TLS1.3
Refer to suggestion: #230

Steps to reproduce:
Secure connection to InfluxDb server from a ESP12 device, 4MB.

Expected behavior:
Not crash, be able to specify buffer sizes and TLS version.
The MFLN should limit the buffer size but not working.

Actual behavior:
OOM crash and writePoint() fails to write the data point due to big buffer and causes crash.
Works if buffer set to 512,512 and TLS1.2

Refer to: #230

Specifications:

• Library Version: 3.13.1
• InfluxDB Version: InfluxDB v2.7.5
• Board/ESP chip: ESP12 4MB
• Device Arduino SDK version: 1.8.19