[fluentd-elasticsearch] Add support for setting the awsSigningSidecar's remote read timeout

[chadlwilson]

What this PR does / why we need it:

Add's support for setting the awsSigningSidecar's remote read timeout, as added in the 1.0 release of aws-es-proxy (which this PR upgrades to)

https://github.com/abutaha/aws-es-proxy/releases/tag/v1.0

Previously the default seemed to be taken from GoLang|OS; leading to ~15 minute downtime if connections to ElasticSearch are terminated/dropped on the remote side; e.g during an AWS ElasticSearch domain upgrade.

The default value chosen in the chart here is the same as the default in the aws-es-proxy code (15 seconds).

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] DCO signed
• [x] Chart Version bumped (if the pr is an update to an existing chart)
• [x] Variables are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [fluentd-elasticsearch])

[chadlwilson]

Thanks a lot @monotek - new chart version is working fine for us :-)