mobile: add knob for h3 keepalive

[danzh2010]

Commit Message: add a config knob to Java, Kotlin and C++ engines to set initial interval of QUIC keepalive probing.

Additional Description: also adjust the validation rule of initial_interval to be larger than 1ms instead of 1s and fix contradicting documentation.

Risk Level: low, interface change Testing: unit test Docs Changes: N/A Release Notes: N/A Platform Specific Features: N/A

[repokitteh-read-only[bot]]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/). envoyproxy/api-shepherds assignee is @abeyad CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/36646 was opened by danzh2010.

see: more, trace.

[abeyad]

test failures look legit though, e.g. https://github.com/envoyproxy/envoy/actions/runs/11369001000/job/31625515074

[repokitteh-read-only[bot]]

no relevant owners for "mobile"

:cat:

Caused by: a https://github.com/envoyproxy/envoy/pull/36646#pullrequestreview-2373219194 was submitted by @abeyad.

see: more, trace.

[abeyad]

/assign @alyssawilk

since it contains core code, Alyssa should merge

[danzh2010]

/retest

[danzh2010]

/retest

[alyssawilk]

/wait-any on CI

[danzh2010]

/retest

[danzh2010]

/assign @envoyproxy/api-shepherds

[repokitteh-read-only[bot]]

@envoyproxy/api-shepherds cannot be assigned to this issue.

:cat:

Caused by: a https://github.com/envoyproxy/envoy/pull/36646#issuecomment-2420148418 was created by @danzh2010.

see: more, trace.

[danzh2010]

@alyssawilk and @abeyad, PTAL again!