feat(confload): add layered configuration loader module

fix(otelx): bypass underlaying lib issue (open-telemetry/opentelemetr…

…y-go#5706)

feat(otelx): support standard OTEL env variables

fix(envx): adjusts the construction of the variable search plan

feat(envx): add source labels support, add ability to specify explici…

…t sources

feat(envx): add sources support, add env file and map sources

fix(envx): use prefixes for error messages

feat(envx): add ability to ignore prefixes

feat(envx): add ability to use custom convert methods