tools: bazel_adaptive: fix pause and downgrade stalls

Allow downgrade to proceed when bazel reported build times exceed the
threshold.

Use process swap in rate as a memory pressure signal.

Bump default downgrade timeout from 100 to 150 seconds and consider
positive progress before abandoning work for a donwgrade.

Lower pause/resume measurement interval from 10 to 3 seconds.

Signed-off-by: Jarno Rajahalme <jarno@isovalent.com>

Author: jrajahalme