Add search query parameter to accounts count endpoints

[cfaur09]

Proposed Changes

• Added support for accounts count/c search filter

How to test

• <api>/accounts/c?search=multiversx
• <api>/accounts/count?search=multiversx

[github-actions]

k6 load testing comparison.
Base Commit Hash: d249093
Target Commit Hash: a0605b5

Metric	Base				Target				Diff
	Avg	Max	90	95	Avg	Max	90	95	Avg	Max	90	95
Pool	47.91	697.35	51.11	53.09	47.22	609.54	50.62	52.08	-1.45% ✅	-12.59% ✅	-0.96% ✅	-1.89% ✅
Mex	47.33	562.23	51.08	53.01	47.16	646.23	50.56	51.99	-0.36% ✅	+14.94% 🔴	-1.02% ✅	-1.93% ✅
Transactions	60.80	2551.41	51.79	55.05	59.69	1651.61	51.30	53.47	-1.83% ✅	-35.27% ✅	-0.94% ✅	-2.87% ✅
Tokens	47.25	351.15	51.06	52.90	47.41	903.34	50.64	52.13	+0.34% 🔴	+157.25% 🔴	-0.82% ✅	-1.47% ✅
Nodes	48.24	935.04	51.04	53.09	46.61	113.90	50.60	52.03	-3.38% ✅	-87.82% ✅	-0.85% ✅	-2.01% ✅
Accounts	48.45	1199.74	51.09	53.08	46.71	165.63	50.55	51.99	-3.58% ✅	-86.19% ✅	-1.05% ✅	-2.05% ✅
Blocks	53.58	1263.20	51.53	56.00	54.34	1348.94	51.12	53.30	+1.42% 🔴	+6.79% 🔴	-0.80% ✅	-4.83% ✅
Test Run Duration	60003.58				60007.27

Legend: Avg - Average Response Time, Max - Maximum Response Time, 90 - 90th Percentile, 95 - 95th Percentile
All times are in milliseconds.