Support the certificate with linebreak strings from env variable

Is your feature request related to a problem? Please describe.

We store the temporal cloud cert and private key as env vars opposed to application.yaml/prop.
Because the env var values cannot contain linebreak/linefeed special characters, the ServiceStubOptionsTemaplte fails to load cert/key saying it is not valid cert on this line .
(It works perfectly with application.yaml/propeties because it converts "\n" to linebreak)

Describe the solution you'd like
Add a logic to convert "\n" to "\n" in the cert string if it is there , maybe in ServiceStubOptionsTemplate class.

Describe alternatives you've considered
I replaced ServiceStubsAutoConfiguration with our customized/extended class which converts "\n" to "\n" in mtlsProperties' cert and key.

@SpringBootApplication(exclude = [ServiceStubsAutoConfiguration::class])

Start in temporal-spring-boot-autoconfigure-alpha/src/main/java/io/temporal/spring/boot/autoconfigure/template/ServiceStubOptionsTemplate.java at the certificate validation line referenced in the issue, and trace how certificate and key values reach it from ServiceStubsAutoConfiguration. Done means certificate and private-key values containing escaped "\n" from environment variables are accepted after conversion to line breaks, while existing application.yaml/properties behavior remains supported.